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Hsiao CT, Chou FC, Hsieh CC, Chang LC, Hsu CM. Developing a Competency-Based Learning and Assessment System for Residency Training: Analysis Study of User Requirements and Acceptance. J Med Internet Res 2020; 22:e15655. [PMID: 32286233 PMCID: PMC7189253 DOI: 10.2196/15655] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 12/17/2019] [Accepted: 02/10/2020] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND The increasingly complex medical environment highlights the importance of milestones and entrustable professional activities (EPAs) to realize the ideals of competency-based medical education (CBME). However, if enormous amounts of assessment results need to be compiled, the development of a digital system to manage, integrate, and synthesize learning and assessment data will be necessary. Furthermore, this system should be able to facilitate real-time assessment with feedback and therefore enhance users' learning through coaching in the moment in the clinical workplace. OBJECTIVE The main purpose of this study was to develop a competency-based electronic platform system to provide resident physicians with clinical assessments and learning in order to enhance the learning of trainees and reduce the burden of assessments. METHODS A competency-based learning and assessment system (CBLAS) for residency training was designed, developed, and evaluated in this study. Opinion interviews and a focus group consensus meeting of key users, including trainees, clinical teachers, and administrative staff, were conducted as needs assessments. The structure of the CBLAS was designed according to the thematic analysis of needs assessments. Clinical teachers' acceptance of using CBME assessments, according to the constructs of attitude, perceived usefulness, and perceived ease of use, was surveyed in the beginning and half a year after implementation of the CBLAS. Additionally, the satisfaction of using the CBLAS, according to information, system, and service qualities, was surveyed after implementation. RESULTS The main functions of the CBLAS, including milestones, EPAs, learning portfolios, teacher/student feedback, e-books, learning materials, assessment progress tracking, and statistical analysis of assessment results, were designed and developed for responding to nine themes, which emerged from the needs assessments of the three user groups. Twenty clinical teachers responded to the CBME assessment acceptance surveys before and after CBLAS implementation, which revealed a significant improvement in the factor of "attitude" (P=.02) but no significant differences in the two factors of "usefulness" (P=.09) and "ease of use" (P=.58) for CBME assessments. Furthermore, satisfaction surveys were performed in 117 users, and 87.2% (102/117) were satisfied with the CBLAS in terms of information, system, and service qualities. There was no significant difference in satisfaction among different user groups. CONCLUSIONS The CBLAS is a user-centered platform that supports clinical teachers' assessment exercises and residents' learning, as well as administrative work for staff according to users' needs assessments and operationalized features of CBME assessments. With the system, clinical teachers had a more positive attitude to conduct the assessment activities of milestones and EPAs and learners could arrange their study schedules to enhance their learning effectiveness. The CBLAS sheds light on how to effectively design and develop a digital system to execute milestone- and EPA-based assessments for enhancing competency-based education among residents, according to our experiences in Taiwan.
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Affiliation(s)
- Cheng-Ting Hsiao
- Department of Emergency Medicine, Chang Gung Memorial Hospital, Puzi City, Chiayi County, Taiwan
- School of Medicine, Chang Gung University, Taoyuan, Taiwan
- Chang Gung Medical Education Research Centre, Taoyuan, Taiwan
| | - Fremen ChihChen Chou
- Center for Faculty Development, Department of Emergency Medicine, China Medical University Hospital, Taichung, Taiwan
- School of Medicine, China Medical University, Taichung, Taiwan
- Department of Emergency Medicine, China Medical University Hospital, Taichung, Taiwan
| | | | - Li Chun Chang
- Nursing, Chang Gung University of Science and Technology, Taoyuan, Taiwan
| | - Chih-Ming Hsu
- Chang Gung Medical Education Research Centre, Taoyuan, Taiwan
- Medical Education Department, Chang Gung Memorial Hospital, Puzi City, Chiayi County, Taiwan
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Kalish S, Chamon C, El-Batanouny M, Santos LH, Sankar R, Chou FC. Contrasting the Surface Phonon Dispersion of Pb_{0.7}Sn_{0.3}Se in Its Topologically Trivial and Nontrivial Phases. Phys Rev Lett 2019; 122:116101. [PMID: 30951360 DOI: 10.1103/physrevlett.122.116101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 02/19/2019] [Indexed: 06/09/2023]
Abstract
We report inelastic He atom scattering measurements of the (001) surface phonon dispersion of the topological crystalline insulator Pb_{0.7}Sn_{0.3}Se. This material exhibits a temperature-dependent topological transition, so we measure the surface dispersion curves in both the trivial and nontrivial phases. We identify that, peculiarly, most surface modes are resonances, rather than pure surface states. We find that a shear vertical surface resonance branch around 9.0 meV dramatically changes on going from the trivial to the topological phase. We associate this remarkable change with the emergence of surface Dirac fermions. We use the measured dispersion of this resonance branch to determine the corresponding mode-dependent electron-phonon coupling λ_{ν}(q).
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Affiliation(s)
- S Kalish
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
| | - C Chamon
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
| | - M El-Batanouny
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
| | - L H Santos
- Institute for Condensed Theory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA and Department of Physics, Emory University, Atlanta, Georgia 30322, USA
| | - R Sankar
- Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - F C Chou
- Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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Chen HW, Chen YW, Kuo JL, Lai YC, Chou FC, Du CH, Liu HL. Spin-charge-lattice coupling in YBaCuFeO 5: Optical properties and first-principles calculations. Sci Rep 2019; 9:3223. [PMID: 30824718 PMCID: PMC6397168 DOI: 10.1038/s41598-019-39031-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 12/10/2018] [Indexed: 11/11/2022] Open
Abstract
We combined spectroscopic ellipsometry, Raman scattering spectroscopy, and first-principles calculations to explore the optical properties of YBaCuFeO5 single crystals. Measuring the optical absorption spectrum of YBaCuFeO5 at room temperature revealed a direct optical band gap at approximately 1.41 eV and five bands near 1.69, 2.47, 3.16, 4.26, and 5.54 eV. Based on first-principles calculations, the observed optical excitations were appropriately assigned. Analysis of the temperature dependence of the band gap indicated anomalies in antiferromagnetic phase transition at 455 and 175 K. Additionally, a hardening in the frequency of the Eg phonon mode was observed at 175 K. The value of the spin-phonon coupling constant was 15.7 mRy/Å2. These results suggest a complex nature of spin-charge-lattice interactions in YBaCuFeO5.
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Affiliation(s)
- H W Chen
- Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan
| | - Y-W Chen
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
| | - J-L Kuo
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
| | - Y C Lai
- Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan
- Department of Physics, Tamkang University, Tamsui, New Taipei City, 25137, Taiwan
| | - F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan
| | - C H Du
- Department of Physics, Tamkang University, Tamsui, New Taipei City, 25137, Taiwan
| | - H L Liu
- Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan.
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Zhang Z, Sutarto R, He F, Chou FC, Udby L, Holm SL, Zhu ZH, Hines WA, Budnick JI, Wells BO. Nematicity and Charge Order in Superoxygenated La_{2-x}Sr_{x}CuO_{4+y}. Phys Rev Lett 2018; 121:067602. [PMID: 30141664 DOI: 10.1103/physrevlett.121.067602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 02/24/2018] [Indexed: 06/08/2023]
Abstract
In this Letter, we report a resonant x-ray scattering measurement of stripelike charge order in the 1/8th doped component of electronically phase-separated, orthorhombic La_{2}CuO_{4+y}. This observation is coupled to the absence of any resonant (001) peak, which at different resonant energies has been identified with the presence of low-temperature-tetragonal-like structural tilt patterns or nematicity in the CuO planes. Thus, we provide evidence that structural pinning is not necessary for the formation of static charge stripes and that the relationship between charge nematicity and stripes may not be simple.
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Affiliation(s)
- Zhiwei Zhang
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - R Sutarto
- Canadian Light Source, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - F He
- Canadian Light Source, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10670, Taiwan
| | - L Udby
- X-ray and Neutron Science, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - S L Holm
- X-ray and Neutron Science, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Z H Zhu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - W A Hines
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - J I Budnick
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
| | - B O Wells
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA
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Sankar R, Peramaiyan G, Muthuselvam IP, Xu S, Hasan MZ, Chou FC. Crystal growth and transport properties of Weyl semimetal TaAs. J Phys Condens Matter 2018; 30:015803. [PMID: 29135472 DOI: 10.1088/1361-648x/aa9a75] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the single crystal growth and transport properties of a Weyl semimetal TaAs. Unsaturated large magnetoresistance of about 22 100% at 2 K and 9 T is observed. From the Hall measurement, carrier concentrations n = 4.608 × 1024 m-3 and p = 3.099 × 1024 m-3, and mobilities µ p = 2.502 m2 V-1 s-1 and µ n = 16.785 m2 V-1 s-1 at 2 K are extracted. The de Haas-van Alphen oscillations at 2 K and 9 T suggest the presence of a Fermi surface, and the quantum electronic parameters such as effective cyclotron mass and Dingle temperature were obtained using Lifshitz-Kosevich fitting. Temperature dependent resistivity measurements at different static magnetic fields suggest the formation of an insulating gap in the Weyl semimetal TaAs. An angle-resolved photoemission spectroscopy study reveals Fermi arc surface states with different shaped features such as a long elliptical contour around each [Formula: see text] point, a bowtie-shaped contour around each [Formula: see text] point, and a crescent-shaped feature near the midpoint of each [Formula: see text] line.
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Affiliation(s)
- Raman Sankar
- Institute of Physics, Academia Sinica, Taipei 10617, Taiwan. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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Sankar R, Rao GN, Muthuselvam IP, Chang TR, Jeng HT, Murugan GS, Lee WL, Chou FC. Anisotropic superconducting property studies of single crystal PbTaSe 2. J Phys Condens Matter 2017; 29:095601. [PMID: 28098075 DOI: 10.1088/1361-648x/aa4edb] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c = 3.83 ± 0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥ to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.
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Affiliation(s)
- Raman Sankar
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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7
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Xu SY, Liu C, Alidoust N, Neupane M, Qian D, Belopolski I, Denlinger JD, Wang YJ, Lin H, Wray LA, Landolt G, Slomski B, Dil JH, Marcinkova A, Morosan E, Gibson Q, Sankar R, Chou FC, Cava RJ, Bansil A, Hasan MZ. Corrigendum: Observation of a topological crystalline insulator phase and topological phase transition in Pb1-xSnxTe. Nat Commun 2016; 7:12505. [PMID: 27489130 PMCID: PMC5155670 DOI: 10.1038/ncomms12505] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Guo ST, Sankar R, Chien YY, Chang TR, Jeng HT, Guo GY, Chou FC, Lee WL. Large transverse Hall-like signal in topological Dirac semimetal Cd3As2. Sci Rep 2016; 6:27487. [PMID: 27263441 PMCID: PMC4893742 DOI: 10.1038/srep27487] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 05/19/2016] [Indexed: 11/30/2022] Open
Abstract
Cadmium arsenide (Cd3As2) is known for its inverted band structure and ultra-high electron mobility. It has been theoretically predicted and also confirmed by ARPES experiments to exhibit a 3D Dirac semimetal phase containing degenerate Weyl nodes. From magneto-transport measurements in high quality single crystals of Cd3As2, a small effective mass m* ≈ 0.05 me is determined from the Shubnikov-de Haas (SdH) oscillations. In certain field orientations, we find a splitting of the SdH oscillation frequency in the FFT spectrum suggesting a possible lifting of the double degeneracy in accord with the helical spin texture at outer and inner Fermi surfaces with opposite chirality predicted by our ab initio calculations. Strikingly, a large antisymmetric magnetoresistance with respect to the applied magnetic fields is uncovered over a wide temperature range in needle crystal of Cd3As2 with its long axis along [112] crystal direction. It reveals a possible contribution of intrinsic anomalous velocity term in the transport equation resulting from a unique 3D Rashba-like spin splitted bands that can be obtained from band calculations with the inclusion of Cd antisite defects.
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Affiliation(s)
- Shih-Ting Guo
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - R Sankar
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.,Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - Yung-Yu Chien
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
| | - Tay-Rong Chang
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Horng-Tay Jeng
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.,Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Guang-Yu Guo
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - Wei-Li Lee
- Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
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9
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Khuntia P, Bert F, Mendels P, Koteswararao B, Mahajan AV, Baenitz M, Chou FC, Baines C, Amato A, Furukawa Y. Spin Liquid State in the 3D Frustrated Antiferromagnet PbCuTe_{2}O_{6}: NMR and Muon Spin Relaxation Studies. Phys Rev Lett 2016; 116:107203. [PMID: 27015508 DOI: 10.1103/physrevlett.116.107203] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Indexed: 06/05/2023]
Abstract
PbCuTe_{2}O_{6} is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu^{2+} ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointing to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T_{1} NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.
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Affiliation(s)
- P Khuntia
- Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, USA
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - F Bert
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - P Mendels
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - B Koteswararao
- School of Physics, University of Hyderabad, Central University PO, Hyderabad 500046, India
- Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - A V Mahajan
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India
| | - M Baenitz
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - F C Chou
- Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - C Baines
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - A Amato
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Y Furukawa
- Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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Ou-Yang TY, Shu GJ, Lin JY, Hu CD, Chou FC. Mn vacancy defects, grain boundaries, and A-phase stability of helimagnet MnSi. J Phys Condens Matter 2016; 28:026004. [PMID: 26683210 DOI: 10.1088/0953-8984/28/2/026004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Mn vacancy defect and grain size are shown to modify the magnetic phase diagram of MnSi significantly, especially near the critical regime of A-phase (skyrmion lattice) formation and the helimagnetic phase transition. Crystals grown using controlled nonstoichiometric initial precursors creates both grain boundaries and intrinsic Mn vacancy defect of various levels in MnSi. The results of combined transport, specific heat, and AC spin susceptibility measurements are compared for MnSi single crystal samples of various manganese deficiency levels and grain sizes. The finite-size effect and Mn vacancy level dependent helical phase transition temperature T(c) have been identified and verified. The stability of A-phase in H-T phase space has been examined through AC spin susceptibility data analysis.
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Affiliation(s)
- T Y Ou-Yang
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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Panneer Muthuselvam I, Sankar R, Ushakov AV, Chen WT, Narsinga Rao G, Streltsov SV, Karna SK, Zhao L, Wu MK, Chou FC. Successive spin orderings of tungstate-bridged Li2Ni(WO4)2 of spin 1. J Phys Condens Matter 2015; 27:456001. [PMID: 26471799 DOI: 10.1088/0953-8984/27/45/456001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Magnetic, thermodynamic, and dielectric properties of Li2Ni(WO4)2 of S = 1 system have been studied using magnetic susceptibility, specific heat, and dielectric constant measurements. The magnetic orderings can be identified in three stages, including a short range magnetic ordering indicated by the rounded χ(T) peak with maximum at ∼20 K, and signatures of two successful antiferromagnetic long range orderings near T(N1) ~ 18 K and T(N2) ~ 13 K revealed by the d(χ(T)) /d(T) peaks. The successive long range magnetic orderings are related to the quasi triangular symmetry breaking in the ac- and bc-planes and to the change of the dielectric constant, suggesting the presence of spin-phonon coupling. The specific heat and magnetic entropy analysis for Li2Ni(WO4)2 shows the existence of a significant low dimensional magnetic correlations at high temperature and confirms the long range three-dimensional (3D) behavior of magnetic orderings below T(N1) and T(N2).
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Affiliation(s)
- I Panneer Muthuselvam
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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12
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Koteswararao B, Panda SK, Kumar R, Yoo K, Mahajan AV, Dasgupta I, Chen BH, Kim KH, Chou FC. Observation of S = 1/2 quasi-1D magnetic and magneto-dielectric behavior in a cubic SrCuTe2O6. J Phys Condens Matter 2015; 27:426001. [PMID: 26436635 DOI: 10.1088/0953-8984/27/42/426001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigate the magnetic, thermal, and dielectric properties of SrCuTe2O6, which is isostructural to PbCuTe2O6, a recently found, Cu-based 3D frustrated magnet with a corner-sharing triangular spin network having dominant first and second nearest neighbor (nn) couplings (Koteswararao et al 2014 Phys. Rev. B 90 035141). Although SrCuTe2O6 has a structurally similar spin network, the magnetic data exhibit the characteristic features of a typical quasi-1D magnet, which mainly resulted from the magnetically dominant third nn coupling, uniform chains. The magnetic properties of this system are studied via magnetization (M), heat capacity (C p ), dielectric constant ([Formula: see text]), and measurements along with ab initio band structure calculations. The magnetic susceptibility [Formula: see text] data show a broad maximum at 32 K and the system orders at low temperatures [Formula: see text] K and [Formula: see text] K, respectively. The analysis of the [Formula: see text] data gives an intra-chain coupling, [Formula: see text], to be about ≈ - 42 K with non-negligible frustrated inter-chain couplings ([Formula: see text] and [Formula: see text]). The hopping parameters obtained from the LDA band structure calculations also suggest the presence of coupled uniform chains. The observation of simultaneous anomalies in [Formula: see text] at [Formula: see text] and [Formula: see text] suggests the presence of a magneto-dielectric effect in SrCuTe2O6. A magnetic phase diagram is also built based on the M, C p , and [Formula: see text] results.
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Affiliation(s)
- B Koteswararao
- School of Physics, University of Hyderabad, Central University PO, Hyderabad 500046, India. CeNSCMR, Department of Physics and Astronomy, and institute of applied physics, Seoul National University, Seoul 151-747, Korea. Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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13
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Udby L, Larsen J, Christensen NB, Boehm M, Niedermayer C, Mohottala HE, Jensen TBS, Toft-Petersen R, Chou FC, Andersen NH, Lefmann K, Wells BO. Measurement of unique magnetic and superconducting phases in oxygen-doped high-temperature superconductors La(2-x)Sr(x)CuO(4+y). Phys Rev Lett 2013; 111:227001. [PMID: 24329465 DOI: 10.1103/physrevlett.111.227001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Indexed: 06/03/2023]
Abstract
We present a combined magnetic neutron scattering and muon spin rotation study of the nature of the magnetic and superconducting phases in electronically phase separated La(2-x)Sr(x)CuO(4+y), x=0.04, 0.065, 0.09. For all samples, we find long-range modulated magnetic order below T(N) is approximately equal to Tc=39 K. In sharp contrast to oxygen-stoichiometric La(2-x)Sr(x)CuO(4), we find that the magnetic propagation vector as well as the ordered magnetic moment is independent of Sr content and consistent with that of the "striped" cuprates. Our study provides direct proof that superoxygenation in La(2-x)Sr(x)CuO(4+y) allows the spin stripe ordered phase to emerge and phase separate from superconducting regions with the hallmarks of optimally doped oxygen-stoichiometric La(2-x)Sr(x)CuO(4).
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Affiliation(s)
- L Udby
- Nanoscience Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - J Larsen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - N B Christensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - M Boehm
- Institut Laue-Langevin, 38042 Grenoble Cedex 9, France
| | - Ch Niedermayer
- Laboratory for Neutron Scattering, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - H E Mohottala
- University of Hartford, West Hartford, Connecticut 06117, USA
| | - T B S Jensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - R Toft-Petersen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark and Helmholtz Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - N H Andersen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - K Lefmann
- Nanoscience Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - B O Wells
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046, USA
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Luo CW, Wang HJ, Ku SA, Chen HJ, Yeh TT, Lin JY, Wu KH, Juang JY, Young BL, Kobayashi T, Cheng CM, Chen CH, Tsuei KD, Sankar R, Chou FC, Kokh KA, Tereshchenko OE, Chulkov EV, Andreev YM, Gu GD. Snapshots of Dirac fermions near the Dirac point in topological insulators. Nano Lett 2013; 13:5797-5802. [PMID: 24228733 DOI: 10.1021/nl4021842] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The recent focus on topological insulators is due to the scientific interest in the new state of quantum matter as well as the technology potential for a new generation of THz optoelectronics, spintronics and quantum computations. It is important to elucidate the dynamics of the Dirac fermions in the topologically protected surface state. Hence we utilized a novel ultrafast optical pump mid-infrared probe to explore the dynamics of Dirac fermions near the Dirac point. The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics. Specifically, the Dirac fermion-phonon coupling strength in the Dirac cone was found to increase from 0.08 to 0.19 while Dirac fermions were away from the Dirac point into higher energy states. Further, the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps. These results are crucial to the design of Dirac fermion devices.
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Affiliation(s)
- C W Luo
- Department of Electrophysics and ‡Institute of Physics, National Chiao Tung University , Hsinchu, Taiwan
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15
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Koteswararao B, Kumar R, Chakraborty J, Jeon BG, Mahajan AV, Dasgupta I, Kim KH, Chou FC. PbCu3TeO7: an S = 1/2 staircase kagome lattice with significant intra-plane and inter-plane couplings. J Phys Condens Matter 2013; 25:336003. [PMID: 23881047 DOI: 10.1088/0953-8984/25/33/336003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have synthesized polycrystalline and single-crystal samples of PbCu3TeO7 and studied its properties via magnetic susceptibility, χ(T), and heat-capacity, Cp(T), measurements and also electronic structure calculations. Whereas the crystal structure is suggestive of the presence of a quasi-2D network of Cu(2+) (S = 1/2) buckled staircase kagome layers, the χ(T) data show magnetic anisotropy and three magnetic anomalies at temperatures TN1 ∼ 36 K, TN2 ∼ 25 K, and TN3 ∼ 17 K. The χ(T) data follow the Curie-Weiss law above 200 K and a Curie-Weiss temperature θCW ∼- 150 K is obtained. The data deviate from the simple Curie-Weiss law below 200 K, which is well above TN1, suggesting the presence of competing magnetic interactions. The magnetic anomaly at TN3 appears to be of first order from magnetization measurements, although our Cp(T) results do not display any anomaly at TN3. The hopping integrals obtained from our electronic structure calculations suggest the presence of significant intra-kagome (next-nearest neighbor and diagonal) and inter-kagome couplings. These couplings take the PbCu3TeO7 system away from a disordered ground state and lead to long-range order, in contrast to what might be expected for an ideal (isotropic) 2D kagome system.
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Affiliation(s)
- B Koteswararao
- Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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16
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Choi KY, Hwang JW, Lemmens P, Wulferding D, Shu GJ, Chou FC. Evidence for dimer crystal melting in the frustrated spin-ladder system BiCu2PO6. Phys Rev Lett 2013; 110:117204. [PMID: 25166571 DOI: 10.1103/physrevlett.110.117204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/19/2013] [Indexed: 06/03/2023]
Abstract
In the spin ladder compound BiCu(2)PO(6), there exists a decisive dynamics of spin excitations that we classify and characterize using inelastic light scattering. We observe an interladder singlet bound mode at 24 cm(-1) and two intraladder bound states at 62 and 108 cm(-1) in the leg (bb) and the rung (cc) polarization as well as a broad triplon continuum extending from 36 cm(-1) to 700 cm(-1). Though isolated spin ladder physics can roughly account for the observed excitations at high energies, frustration and interladder interactions need to be considered to fully describe the spectral distribution and scattering selection rules at low and intermediate energies. In addition, we attribute the rich spectrum of singlet bound modes to a melting of a dimer crystal. Our study provides evidence for a Z(2) quantum phase transition from a dimer to a resonating valence bond state driven by singlet fluctuations.
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Affiliation(s)
- K-Y Choi
- Department of Physics, Chung-Ang University, 221 Huksuk-Dong, Seoul 156-756, Republic of Korea
| | - J W Hwang
- Department of Physics, Chung-Ang University, 221 Huksuk-Dong, Seoul 156-756, Republic of Korea
| | - P Lemmens
- Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany
| | - D Wulferding
- Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany
| | - G J Shu
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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17
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Shu GJ, Hsu SL, Chu MW, Lee CC, Chou FC. Site occupancy and magnetic properties of pyrochlore-structured AgOs2O6. J Phys Condens Matter 2012; 24:385701. [PMID: 22944887 DOI: 10.1088/0953-8984/24/38/385701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
AgOs(2)O(6) prepared from ion-exchanged superconducting β-pyrochlore KOs(2)O(6) has been shown to be non-superconducting. Synchrotron x-ray structure refinement suggests that AgOs(2)O(6) has the Ag ion mostly occupying the low-symmetry 32e site in the [Formula: see text] space group of proper occupancy, which is different from the original major occupancy at the high-symmetry 8b site for KOs(2)O(6), and similar to non-superconducting Na(1.4)Os(2)O(6)·H(2)O. Magnetic susceptibility measurements found no magnetic ordering down to ~1.7 K. The trace amount of isolated spins suggests that the Ag could be neutral and lead to a pure Os(6+) valence state of zero spin in the newly prepared AgOs(2)O(6).
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Affiliation(s)
- G J Shu
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
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18
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Zhu X, Santos L, Howard C, Sankar R, Chou FC, Chamon C, El-Batanouny M. Electron-phonon coupling on the surface of the topological insulator Bi2Se3 determined from surface-phonon dispersion measurements. Phys Rev Lett 2012; 108:185501. [PMID: 22681089 DOI: 10.1103/physrevlett.108.185501] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Indexed: 06/01/2023]
Abstract
In this Letter, we report measurements of the coupling between Dirac fermion quasiparticles (DFQs) and phonons on the (001) surface of the strong topological insulator Bi2Se3. While most contemporary investigations of this coupling have involved examining the temperature dependence of the DFQ self-energy via angle-resolved photoemission spectroscopy measurements, we employ inelastic helium-atom scattering to explore, for the first time, this coupling from the phonon perspective. Using a Hilbert transform, we are able to obtain the imaginary part of the phonon self-energy associated with a dispersive surface-phonon branch identified in our previous work [Phys. Rev. Lett. 107, 186102 (2011)] as having strong interactions with the DFQs. From this imaginary part of the self-energy we obtain a branch-specific electron-phonon coupling constant of 0.43, which is stronger than the values reported from the angle-resolved photoemission spectroscopy measurements.
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Affiliation(s)
- Xuetao Zhu
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
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19
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Zhu X, Santos L, Sankar R, Chikara S, Howard C, Chou FC, Chamon C, El-Batanouny M. Interaction of phonons and dirac fermions on the surface of Bi2Se3: a strong Kohn anomaly. Phys Rev Lett 2011; 107:186102. [PMID: 22107648 DOI: 10.1103/physrevlett.107.186102] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Indexed: 05/31/2023]
Abstract
We report the first measurements of phonon dispersion curves on the (001) surface of the strong three-dimensional topological insulator Bi2Se3. The surface phonon measurements were carried out with the aid of coherent helium beam surface scattering techniques. The results reveal a prominent signature of the exotic metallic Dirac fermion quasiparticles, including a strong Kohn anomaly. The signature is manifest in a low energy isotropic convex dispersive surface phonon branch with a frequency maximum of 1.8 THz and having a V-shaped minimum at approximately 2kF that defines the Kohn anomaly. Theoretical analysis attributes this dispersive profile to the renormalization of the surface phonon excitations by the surface Dirac fermions. The contribution of the Dirac fermions to this renormalization is derived in terms of a Coulomb-type perturbation model.
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Affiliation(s)
- Xuetao Zhu
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
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20
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Clancy JP, Gaulin BD, Adams CP, Granroth GE, Kolesnikov AI, Sherline TE, Chou FC. Singlet-triplet excitations in the unconventional spin-Peierls TiOBr compound. Phys Rev Lett 2011; 106:117401. [PMID: 21469893 DOI: 10.1103/physrevlett.106.117401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Indexed: 05/30/2023]
Abstract
We have performed time-of-flight neutron scattering measurements on powder samples of the unconventional spin-Peierls compound TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the Spallation Neutron Source at Oak Ridge National Laboratory. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate spin-Peierls phases, which we associate with n=1 and n=2 triplet excitations out of the singlet ground state. These results represent the first direct measurement of the singlet-triplet energy gap in TiOBr, which has a value of E(g)=21.2±1.0 meV.
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Affiliation(s)
- J P Clancy
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada
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21
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Huang SH, Chu CH, Yu JC, Chuang WC, Lin GJ, Chen PL, Chou FC, Chau LY, Sytwu HK. Transgenic expression of haem oxygenase-1 in pancreatic beta cells protects non-obese mice used as a model of diabetes from autoimmune destruction and prolongs graft survival following islet transplantation. Diabetologia 2010; 53:2389-400. [PMID: 20683574 DOI: 10.1007/s00125-010-1858-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 07/05/2010] [Indexed: 01/05/2023]
Abstract
AIMS/HYPOTHESIS Haem oxygenase 1 (HO-1) has strong anti-apoptotic, anti-inflammatory and antioxidative effects that help protect cells against various forms of immune attack. We investigated whether transgenic expression of Ho-1 (also known as Hmox1) in pancreatic beta cells would protect NOD mice from autoimmune damage and prolong graft survival following islet transplantation. METHODS To evaluate the protective effect of beta cell-specific HO-1 in autoimmune diabetes, we used an insulin promoter-driven murine Ho-1 construct (pIns-mHo-1) to generate a transgenic NOD mouse. Transgene expression, insulitis and the incidence of diabetes in mice were characterised. Lymphocyte composition, the development of T helper (Th)1, Th2 and T regulatory (Treg) cells, T cell proliferation and lymphocyte-mediated disease transfer were analysed. The potential effects of transgenic islets and islet transplantation on apoptosis, inflammation and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) were evaluated. RESULTS Transgenic mice showed less severe insulitis and a lower incidence of diabetes than non-transgenic control littermates. Lymphocyte composition and functions were not affected. Islets from transgenic mice expressed lower levels of proinflammatory cytokines/chemokines, proapoptotic gene expression and amounts of ROS/RNS, and were more resistant to TNF-α- and IFN-γ-induced apoptosis. Islet grafts from transgenic mice also survived longer in diabetic recipients than control islets. CONCLUSIONS/INTERPRETATION Transgenic overexpression of Ho-1 in beta cells protected NOD mice from diabetes and delayed the autoimmune destruction of islet grafts, providing valuable insight into the development of better strategies for clinical islet transplantation in patients with type 1 diabetes.
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Affiliation(s)
- S H Huang
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China
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22
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Huang FT, Gloter A, Chu MW, Chou FC, Shu GJ, Liu LK, Chen CH, Colliex C. Scanning transmission electron microscopy using selective high-order laue zones: three-dimensional atomic ordering in sodium cobaltate. Phys Rev Lett 2010; 105:125502. [PMID: 20867654 DOI: 10.1103/physrevlett.105.125502] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Indexed: 05/29/2023]
Abstract
A new scanning transmission electron microscopy (STEM) imaging technique using high-order Laue zones (named HOLZ-STEM), a diffraction contrast which has been strenuously avoided or minimized in traditional STEM imaging, can be used to obtain the additional 1D periodic information along the electron propagation axis without sacrificing atomic resolution in the lateral (2D) dimension. HOLZ-STEM has been demonstrated to resolve the 3D long-range Na ordering of Na0.71CoO2. Direct evidence of spiral-like Na-trimer chains twisting along the c axis is unambiguously established in real space.
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Affiliation(s)
- F-T Huang
- Laboratoire de Physique des Solides, Université Paris-Sud, CNRS-UMR 8502, Orsay, France
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23
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Chou FC, Chu MW, Shu GJ, Huang FT, Pai WW, Sheu HS, Lee PA. Sodium ion ordering and vacancy cluster formation in NaxCoO2 (x=0.71 and 0.84) single crystals by synchrotron X-Ray diffraction. Phys Rev Lett 2008; 101:127404. [PMID: 18851411 DOI: 10.1103/physrevlett.101.127404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Indexed: 05/26/2023]
Abstract
In the rich phase diagram of NaxCoO2, x=0.71 enjoys special stability and is called the Curie-Weiss metal due to its anomalous properties. Similarly, x=0.84 prepared from high temperature melt is a special end point beyond which the system phase separates. Using synchrotron x-ray diffraction on single crystals, we discovered sqrt[12]a and sqrt[13]a superlattice structures which we interpret as the ordering of Na (vacancy) clusters. These results lead to a picture of coexisting local moments and itinerant carriers and form the first step towards understanding the many anomalous properties of cobaltates.
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Affiliation(s)
- F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan.
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24
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Huang SW, Huang DJ, Okamoto J, Mou CY, Wu WB, Yeh KW, Chen CL, Wu MK, Hsu HC, Chou FC, Chen CT. Magnetic ground state and transition of a quantum multiferroic LiCu2O2. Phys Rev Lett 2008; 101:077205. [PMID: 18764576 DOI: 10.1103/physrevlett.101.077205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Indexed: 05/26/2023]
Abstract
Based on resonant soft x-ray magnetic scattering, we report that LiCu2O2 exhibits a large interchain coupling which suppresses quantum fluctuations along spin chains, and a quasi-2D short-range magnetic order prevails at temperatures above the magnetic transition. These observations unravel the fact that the ground state of LiCu2O2 possesses long-range 2D-like incommensurate magnetic order rather than being a gapped spin liquid as expected from the nature of quantum spin-1/2 chains. In addition, the spin coupling along the c axis is found to be essential for inducing electric polarization.
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Affiliation(s)
- S W Huang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
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25
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Pai WW, Huang SH, Meng YS, Chao YC, Lin CH, Liu HL, Chou FC. Sodium trimer ordering on a NaxCoO2 surface. Phys Rev Lett 2008; 100:206404. [PMID: 18518561 DOI: 10.1103/physrevlett.100.206404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Indexed: 05/26/2023]
Abstract
Sodium ion ordering on an in situ cleaved NaxCoO2 (x=0.84) surface has been studied by ultrahigh vacuum scanning tunneling microscopy at room temperature. Three main phases, with p(3 x 3), ( radical7 x radical7), and (2 radical3 x 2 radical3) hexagonal unit cells and a surface Na concentration of 1/3, 3/7, 1/2, respectively, were identified. One surprising finding is that Na trimers act as the basic building blocks that order in long range. The stability of Na trimers is attributed to the increased Na coordination with oxygen as indicated by ab initio calculations, and possibly at finite temperature by configuration entropy.
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Affiliation(s)
- Woei Wu Pai
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan, Republic of China.
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26
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Balicas L, Jo YJ, Shu GJ, Chou FC, Lee PA. Local moment, itinerancy, and deviation from Fermi-liquid behavior in NaxCoO2 for 0.71< or = x < or =0.84. Phys Rev Lett 2008; 100:126405. [PMID: 18517893 DOI: 10.1103/physrevlett.100.126405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Indexed: 05/26/2023]
Abstract
Here we report the observation of Fermi surface (FS) pockets via the Shubnikov-de Haas effect in NaxCoO2 for x=0.71 and 0.84, respectively. Our observations indicate that the FS expected for each compound intersects their corresponding Brillouin zones, as defined by the previously reported superlattice structures, leading to small reconstructed FS pockets, but only if a precise number of holes per unit cell is localized. For 0.71< or = x < 0.75 the coexistence of itinerant carriers and localized S=1/2 spins on a paramagnetic triangular superlattice leads at low temperatures to the observation of a deviation from standard Fermi-liquid behavior in the electrical transport and heat capacity properties, suggesting the formation of some kind of quantum spin-liquid ground state.
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Affiliation(s)
- L Balicas
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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27
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Ning FL, Golin SM, Ahilan K, Imai T, Shu GJ, Chou FC. 59Co NMR evidence for charge ordering below T_(CO) approximately 51 K in Na0.5CoO2. Phys Rev Lett 2008; 100:086405. [PMID: 18352643 DOI: 10.1103/physrevlett.100.086405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2007] [Indexed: 05/26/2023]
Abstract
The CoO2 layers in NaxCoO2 may be viewed as a spin S=1/2 triangular-lattice doped with charge carriers. The underlying physics of the cobaltates is very similar to that of the high T_(c) cuprates. We will present unequivocal 59Co NMR evidence that below T_(CO) approximately 51 K, the insulating ground state of the itinerant antiferromagnet Na0.5CoO2 (T_(N) approximately 86 K) is induced by charge ordering.
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Affiliation(s)
- F L Ning
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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28
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Balicas L, Analytis JG, Jo YJ, Storr K, Zandbergen H, Xin Y, Hussey NE, Chou FC, Lee PA. Shubnikov-de Haas effect in the metallic state of Na0.3CoO2. Phys Rev Lett 2006; 97:126401. [PMID: 17025986 DOI: 10.1103/physrevlett.97.126401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Indexed: 05/12/2023]
Abstract
Shubnikov-de Haas oscillations for two well-defined frequencies, corresponding, respectively, to areas of 0.8 and 1.36% of the first Brillouin zone, were observed in single crystals of Na(0.3)CoO2. The existence of Na superstructures in Na0.3CoO2, coupled with this observation, suggests the possibility that the periods are due to the reconstruction of the large Fermi surface around the Gamma point. An alternative interpretation in terms of the long sought-after epsilon'(g) pockets is also considered but found to be incompatible with existing specific heat data.
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Affiliation(s)
- L Balicas
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306, USA
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29
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Lisunov KG, Arushanov E, Raquet B, Broto JM, Chou FC, Wizent N, Behr G. Hopping conductivity in CaCu(2)O(3) single crystals. J Phys Condens Matter 2006; 18:8541-8549. [PMID: 21690907 DOI: 10.1088/0953-8984/18/37/012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The resistivity, ρ, of the spin-ladder compound CaCu(2)O(3) is investigated between T∼130-450 K. The ρ(T) data measured for [Formula: see text] (along the Cu-O-Cu leg) and [Formula: see text] (along the Cu-O-Cu rungs), ρ(a)(T)>ρ(b)(T), exhibit an activated dependence, similar in both directions and characterized by a nearest-neighbour hopping followed by a variable-range hopping (VRH) regime when T is decreased. A detailed analysis of ρ(T) demonstrates that conventional d-dimensional models of the hopping conductivity, based on the electron localization in disordered systems, cannot interpret the experimental data at any d = 1, 2 or 3, leading to the mismatch of the characteristic energies and/or unphysical values of the characteristic length scales. The observed VRH conductivity law on the low-temperature interval, lnρ∼T(-3/4), contradicts the models above, too. Instead, it is found that this law can be substantiated and the correct matching of the energy and length scales can be found within a model of Fogler et al (2004 Phys. Rev. B 69 035413) by treating CaCu(2)O(3) as a three-dimensional array of quasi-one-dimensional electron crystals.
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Affiliation(s)
- K G Lisunov
- Institute of Applied Physics, Academy of Sciences of Moldova, Academiei Street 5, MD-2028 Kishinev, Moldova
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30
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Lemmens P, Choi KY, Gnezdilov V, Sherman EY, Chen DP, Lin CT, Chou FC, Keimer B. Anomalous electronic Raman scattering in NaxCoO2.yH2O. Phys Rev Lett 2006; 96:167204. [PMID: 16712268 DOI: 10.1103/physrevlett.96.167204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Indexed: 05/09/2023]
Abstract
Raman scattering experiments on NaxCoO2.yH2O single crystals show a broad electronic continuum with a pronounced peak around 100 cm(-1) and a cutoff at approximately 560 cm(-1) over a wide range of doping levels. The electronic Raman spectra in superconducting and nonsuperconducting samples are similar at room temperature, but evolve in markedly different ways with decreasing temperature. For superconducting samples, the low-energy spectral weight is depleted upon cooling below T* approximately 150 K, indicating the opening of a pseudogap that is not present in nonsuperconducting materials. Weak additional phonon modes observed below T* suggest that the pseudogap is associated with charge ordering.
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Affiliation(s)
- P Lemmens
- Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany and Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany
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31
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Gasparović G, Ott RA, Cho JH, Chou FC, Chu Y, Lynn JW, Lee YS. Neutron scattering study of novel magnetic order in Na0.5CoO2. Phys Rev Lett 2006; 96:046403. [PMID: 16486856 DOI: 10.1103/physrevlett.96.046403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Indexed: 05/06/2023]
Abstract
We report polarized and unpolarized neutron scattering measurements of the magnetic order in single crystals of Na0.5CoO2. Our data indicate that below TN=88 K the spins form a novel antiferromagnetic pattern within the CoO2 planes, consisting of alternating rows of ordered and nonordered Co ions. The domains of magnetic order appear to be closely coupled to the domains of Na ion order, consistent with such a twofold symmetric spin arrangement. Magnetoresistance and anisotropic susceptibility measurements further support this model for the electronic ground state.
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Affiliation(s)
- G Gasparović
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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32
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Balicas L, Abdel-Jawad M, Hussey NE, Chou FC, Lee PA. Shubnikov-de Haas oscillations and the magnetic-field-induced suppression of the charge ordered state in Na(0.5)CoO2. Phys Rev Lett 2005; 94:236402. [PMID: 16090488 DOI: 10.1103/physrevlett.94.236402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Indexed: 05/03/2023]
Abstract
We have performed electrical transport measurements at low temperatures and high magnetic fields in Na(0.5)CoO2 single crystals. Shubnikov-de Haas oscillations corresponding to only 1% of the area of the orthorhombic Brillouin zone were clearly observed, indicating that most of the original Fermi surface vanishes at the charge-ordering (CO) transition. In-plane magnetic fields were found to suppress strongly the CO state. For fields rotated within the conducting planes, we observe angular magnetoresistance oscillations whose periodicity changes from twofold to sixfold at the transition.
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Affiliation(s)
- L Balicas
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
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Wu WB, Huang DJ, Okamoto J, Tanaka A, Lin HJ, Chou FC, Fujimori A, Chen CT. Orbital symmetry and electron correlation in NaxCoO2. Phys Rev Lett 2005; 94:146402. [PMID: 15904085 DOI: 10.1103/physrevlett.94.146402] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2004] [Indexed: 05/02/2023]
Abstract
Measurements of polarization-dependent soft x-ray absorption reveal that the electronic states determining the low-energy excitations of NaxCoO2 have predominantly a(1g) symmetry with significant O 2p character. In contrast to the prediction of band theory, doping-dependent O 1s x-ray absorption shows a large transfer of spectral weight, providing spectral evidence for strong electron correlations of the layered cobaltates. We also found that NaxCoO2 exhibits a charge-transfer electronic character rather than a Mott-Hubbard character.
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Affiliation(s)
- W B Wu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
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Ning FL, Imai T, Statt BW, Chou FC. Spin dynamics in the carrier-doped S=1/2 triangular lattice of NaxCoO2.yH2O. Phys Rev Lett 2004; 93:237201. [PMID: 15601195 DOI: 10.1103/physrevlett.93.237201] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Indexed: 05/24/2023]
Abstract
We probed the local electronic properties of the mixed-valent Co+4-x triangular lattice in NaxCoO2.yH(2)O by 59Co NMR. We observed two distinct types of Co sites for x > or =1/2, but the valence seems averaged out for x approximately 1/3. Local spin fluctuations exhibit qualitatively the same trend down to approximately 100 K regardless of the carrier concentration x, and hence the nature of the electronic ground state. A canonical Fermi-liquid behavior emerges below approximately 100 K only for x approximately 1/3.
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Affiliation(s)
- F L Ning
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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Chang YT, Shiao YM, Chin PJ, Liu YL, Chou FC, Wu S, Lin YF, Li LH, Lin MW, Liu HN, Tsai SF. Genetic polymorphisms of the HCR gene and a genomic segment in close proximity to HLA-C are associated with patients with psoriasis in Taiwan. Br J Dermatol 2004; 150:1104-11. [PMID: 15214895 DOI: 10.1111/j.1365-2133.2004.05972.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND Although psoriasis vulgaris (PV) is strongly associated with HLA-Cw*0602, it has been proposed that the association of Cw*0602 is due to linkage disequilibrium and that other nearby genes are involved in PV susceptibility. The alpha-helix coiled-coil rod homologue (HCR) gene, located 110 kb telomeric to the HLA-C locus, is presumed to be one of the PV candidate genes. Recently, a 10-kb genomic segment, centromeric to HLA-C, defined by two new single nucleotide polymorphisms (SNPs) n.7*A and n.9*C, was found to have a stronger association with psoriasis than the HCR gene. Until now, no study of the association of the HCR gene, SNPs n.7, and n.9 has been conducted on Chinese patients with psoriasis. OBJECTIVES We aimed to determine whether the genetic polymorphisms of the HCR gene, SNPs n.7*A, and n.9*C were associated with an increased risk of psoriasis in Chinese patients. METHODS Using direct sequencing of the HCR gene and the genomic region containing SNPs n.7 and n.9, we investigated the HCR gene, SNPs n.7, and n.9 for disease association in 115 Chinese patients with psoriasis and 103 control subjects. The HCR SNPs were confirmed by denaturing high performance liquid chromatography. Genotyping for HLA-Cw*0602 was also carried out using sequence-based typing. RESULTS We observed a different allelic distribution between patient and control groups at nucleotide positions 386, 404, 1802 and 2406 of the HCR gene, and SNPs n.7, and n.9. The associations were much stronger in early onset PV patients (for HCR-386*T and HCR-404*T, odds ratio = 5.63, Pc < 0.0001). The HLA-Cw*0602 also displayed a similar association with PV (odds ratio = 5.4, Pc < 0.0001). Moreover, SNP n.7*A, SNP n.9*C, Cw*0602, HCR-386*T, HCR-404*T and HCR-1802*T were in linkage disequilibrium with each other. Haplotype-based association analysis showed SNP n.7*A-SNP n.9*C-Cw*0602-HCR-386*T-HCR-404*T-HCR-1802*T-HCR-2406*G as a major susceptibility haplotype in this Chinese population (for early onset patients, odds ratio = 5.15, Pc < 0.0001). CONCLUSIONS Our results indicate that the HCR gene, SNP n.7*A, and SNP n.9*C as well as Cw*0602 are major susceptibility markers for psoriasis in Chinese patients.
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Affiliation(s)
- Y T Chang
- Department of Dermatology, National Yang-Ming University, Taipei, Taiwan, Republic of China.
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Chou FC, Cho JH, Lee PA, Abel ET, Matan K, Lee YS. Thermodynamic and transport measurements of superconducting Na0.3CoO2.1.3H2O single crystals prepared by electrochemical deintercalation. Phys Rev Lett 2004; 92:157004. [PMID: 15169310 DOI: 10.1103/physrevlett.92.157004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Indexed: 05/24/2023]
Abstract
Superconducting single crystal samples of Na0.3CoO2.1.3H(2)O have been produced using an electrochemical technique which dispenses with the usual bromine chemical deintercalation method. In fully hydrated crystals, susceptibility and specific heat measurements confirm that bulk superconductivity has been achieved. The extracted normal state density of states indicates Fermi-liquid behavior with strong mass enhancement and a modest Wilson ratio. Measurements of H(c2) for H parallel c and H parallel ab reveal significant anisotropy, and the extracted value for the coherence length is about 100 A, consistent with an extremely narrow bandwidth.
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Affiliation(s)
- F C Chou
- Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Thurber KR, Hunt AW, Imai T, Chou FC. 17O NMR study of q = 0 spin excitations in a nearly ideal S = 1 / 2 1D Heisenberg antiferromagnet, Sr2CuO3, up to 800 K. Phys Rev Lett 2001; 87:247202. [PMID: 11736538 DOI: 10.1103/physrevlett.87.247202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2001] [Indexed: 05/23/2023]
Abstract
We used 17O NMR to probe the uniform (wave vector q = 0) electron spin excitations up to 800 K in Sr2CuO3 and separate the q = 0 from the q = +/-pi / a staggered components. Our results support the logarithmic decrease of the uniform spin susceptibility below T approximately 0.015J, where J = 2200 K. From measurement of the dynamical spin susceptibility for q = 0 by the spin-lattice relaxation rate 1/T(1), we demonstrate that the q = 0 mode of spin transport is ballistic at the T = 0 limit, but has a diffusion-like contribution at finite temperatures even for T<<J.
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Affiliation(s)
- K R Thurber
- Department of Physics, MIT, Cambridge, Massachusetts 02139 and Center for Materials Science and Engineering, MIT, Cambridge, Massachusetts 02139
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Chou FC, Tzeng SJ, Huang JD. Genetic polymorphism of cytochrome P450 3A5 in Chinese. Drug Metab Dispos 2001; 29:1205-9. [PMID: 11502729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
The CYP3A subfamily enzymes are the most abundant and important drug-metabolizing enzymes. Wide variation in the CYP3A5 expression was well known. Recently, G(-44) to A of CYP3AP1 was found to segregate with CYP3A5*3 defective allele. The homozygous A(-44) subjects showed low expression of CYP3A5. In Caucasian, only 9.2% of CYP3AP1 alleles were with G(-44) and associated with the wild-type CYP3A5*1 allele, which expressed CYP3A5 significantly. By using polymerase chain reaction and FauI endonuclease digestion, we found that 28% of CYP3AP1 alleles are G(-44) in 110 Chinese subjects. The frequency is 3 times higher in Chinese than in Caucasian, implying more Chinese subjects are probably extensive CYP3A5 metabolizers. In two Chinese subjects, we also found a heterozygous G(13048)gt-to-G(13048)gc mutation at the intron 5 splicing donor site, leading to a splicing defect. A 6478-base pair minigene, including intron 4 to intron 7, was used for in vitro transcription. Both the wild-type and the mutated minigenes produced splicing variants. The wild-type minigene used Ggt(13050) as the splicing donor. The mutant minigene used gt(8504) in intron 4 or gt(13112) in intron 5 as the splicing donor for various splicing acceptors. The splicing defect may result in a shorter peptide or cause the frame shift. In the other two Chinese subjects, we found A(14763)-to-G mutation in exon 7, resulting in the Q200R amino acid change. The consequence of the polymorphism site has not been known. In Caucasian, there is a reported T398N polymorphism. In these Chinese subjects, we did not find polymorphism at this site.
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Affiliation(s)
- F C Chou
- Department of Pharmacology, College of Medicine, National Cheng Kung University, Medical Center, 1 University Road, Tainan 70101, Taiwan
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Wu S, Shiao YM, Lai SM, Lai CY, Chen SP, Chen YF, Sidebottom DA, Hildebrand WH, Chou FC, Tsai MF. New DR5 sequences: a novel DRB1*11122 allele identified in Paiwan tribe members of Taiwan and a corrected sequence for the DRB1*1201 allele. Tissue Antigens 2001; 58:193-7. [PMID: 11703830 DOI: 10.1034/j.1399-0039.2001.580310.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We report herein the identification of a new DRB1 allele using sequence-based typing (SBT). This novel allele, HLA-DRB1*11122, was found in an aboriginal individual (SWP71) from the Paiwan tribe in the southern part of Taiwan. This individual was typed by SBT method as having an HLA genotype of HLA-A*24021/24021, HLA-B*4001/4002, HLA-DRB1*11122/15011, HLA-DRB3*0202, and HLA-DRB5*01011. This new allele differs from DRB1*1112 in the polymorphic exon 2 only at codon 34 (CAA-->CAG; both specify glutamine) and from DRB1*1110 in the exon 2 sequence only at codon 32 (CAT-->TAT; H32T). The most likely candidate allele which is found in the aboriginal populations of Taiwan and which may mutate into this new allele is DRB1*11011. DRB1*11122 allele differs from DRB1*11011 allele in the polymorphic exon 2 at both codon 34 (CAA-->CAG) and codon 37 (TAC-->TTC; T37F). This novel HLA-DRB1*11122 allele was also found in another aboriginal individual (SWP90) from the same Paiwan tribe. This SWP90 individual was typed by SBT method as having an HLA genotype of HLA-A*24021/24021, HLA-B*4002/5502, HLA-DRB1*11122/1201, and HLA-DRB3*01011/0202. However, the original DRB1*1201 sequence from HERLUFF was found to be erroneously reported and the corrected sequence from SWP90 is now presented herein.
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Affiliation(s)
- S Wu
- Graduate Institute of Human Genetics/Department of Medical Technology, Tzu Chi University, #701, Chung Yang Rd. Section III, Hualien, Taiwan, Republic of China.
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Kim YJ, Birgeneau RJ, Chou FC, Erwin RW, Kastner MA. Critical spin dynamics of the 2D quantum Heisenberg antiferromagnets Sr2CuO2Cl2 and Sr2Cu3O4Cl2. Phys Rev Lett 2001; 86:3144-3147. [PMID: 11290128 DOI: 10.1103/physrevlett.86.3144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2000] [Indexed: 05/23/2023]
Abstract
We report a neutron scattering study of the long-wavelength dynamic spin correlations in the model two-dimensional S = 1/2 square lattice Heisenberg antiferromagnets Sr2CuO2Cl2 and Sr2Cu3O4Cl2. The characteristic energy scale, omega(0)(T/J), is determined by measuring the quasielastic peak width in the paramagnetic phase over a wide range of temperature ( 0.2 less similarT/J less similar0.7). The obtained values for omega(0)(T/J) agree quantitatively between the two compounds and also with values deduced from quantum Monte Carlo simulations. The combined data show scaling behavior, omega approximately xi(-z), over the entire temperature range with z = 1.0(1), in agreement with dynamic scaling theory.
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Affiliation(s)
- Y J Kim
- Department of Physics and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge 02139, USA
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Wu S, Shiao YM, Lai CY, Lai SM, Chen SP, Sidebottom DA, Hildebrand WH, Tilanus MG, Chou FC, Tsai MF. Polymorphism of human HLA-DRB1 antigens generated by genetic exchange between DR2 (DRB1*15011) and DR6 (DRB1*1405) alleles: a novel DRB1 allele (DRB1*1437) identified in a Paiwan tribe member of Taiwan. Tissue Antigens 2001; 57:384-7. [PMID: 11380954 DOI: 10.1034/j.1399-0039.2001.057004384.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We report herein the identification of a new DRB1 allele using sequence-based typing (SBT). This novel allele, HLA-DRB1*1437, was found in an aboriginal individual from the Paiwan tribe in the southern part of Taiwan. This individual was typed by SBT method as having an HLA genotype of HLA-A*02011/0203, HLA-B*15011/3901, HLA-DRB1*11011/1437, HLA-DRB3*0202/0202, and HLA-DPB1*0501/1301. This new allele differs from DRB1*1309 in the 5'-end nucleotide sequence of polymorphic exon 2 at codon 16 (CAT-->CAA; H16Q), codon 37 (AAC-->TTC; R37F), codon 47 (TTC-->TAC; F47Y), and codon 58 (GCC-->GCT; both specify alanine). By sequence comparison, it was found that this new allele has a 5'-end sequence (from amino acid residues 7 to 66) identical to that found in the DRB1*1405 allele and a 3'-end sequence (from amino acid residues 58 to 94) identical to that found in the DRB1*15011 allele. Both DRB1*1405 and DRB1*15011 alleles have been identified among the Paiwan members (Note).
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Affiliation(s)
- S Wu
- Tzu Chi University, Hualien, Taiwan, Republic of China.
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Thurber KR, Imai T, Saitoh T, Azuma M, Takano M, Chou FC. 63Cu NQR evidence of dimensional crossover to anisotropic 2D regime in S = 1 / 2 three-Leg ladder Sr2Cu3O5. Phys Rev Lett 2000; 84:558-561. [PMID: 11015963 DOI: 10.1103/physrevlett.84.558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/1999] [Indexed: 05/23/2023]
Abstract
We probed spin-spin correlations up to 725 K with 63Cu nuclear quadrupole resonance in the S = 1 / 2 three-leg ladder Sr2Cu3O5. We present experimental evidence that below 300 K weak interladder coupling causes dimensional crossover of the spin-spin correlation length xi from the quasi-1D (xi approximately 1 / T) to the anisotropic 2D regime ( xi approximately exp2pirho(s) / T, where 2pirho(s) = 290+/-30 K is the effective spin stiffness).
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Affiliation(s)
- KR Thurber
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Chou FC, Johnston DC. Phase separation and oxygen diffusion in electrochemically oxidized La2CuO4+ delta : A static magnetic susceptibility study. Phys Rev B Condens Matter 1996; 54:572-583. [PMID: 9984293 DOI: 10.1103/physrevb.54.572] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Statt BW, Hammel PC, Fisk Z, Cheong SW, Chou FC, Johnston DC, Schirber JE. Oxygen ordering and phase separation in La2CuO4+ delta. Phys Rev B Condens Matter 1995; 52:15575-15581. [PMID: 9980918 DOI: 10.1103/physrevb.52.15575] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Quijada MA, Tanner DB, Chou FC, Johnston DC, Cheong S. Optical properties of single-crystal La2CuO4+ delta. Phys Rev B Condens Matter 1995; 52:15485-15503. [PMID: 9980906 DOI: 10.1103/physrevb.52.15485] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Borsa F, Carreta P, Cho JH, Chou FC, Hu Q, Johnston DC, Lascialfari A, Torgeson DR, Gooding RJ, Salem NM, Vos KJ. Staggered magnetization in La2-xSrxCuO4 from 139La NQR and microSR: Effects of Sr doping in the range 0<x<0.02. Phys Rev B Condens Matter 1995; 52:7334-7345. [PMID: 9979677 DOI: 10.1103/physrevb.52.7334] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Radaelli PG, Jorgensen JD, Kleb R, Hunter BA, Chou FC, Johnston DC. Miscibility gap in electrochemically oxygenated La2CuO4+ delta. Phys Rev B Condens Matter 1994; 49:6239-6245. [PMID: 10011609 DOI: 10.1103/physrevb.49.6239] [Citation(s) in RCA: 118] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Chou FC, Borsa F, Cho JH, Johnston DC, Lascialfari A, Torgeson DR, Ziolo J. Magnetic phase diagram of lightly doped La2-xSrxCuO4 from 139La nuclear quadrupole resonance. Phys Rev Lett 1993; 71:2323-2326. [PMID: 10054644 DOI: 10.1103/physrevlett.71.2323] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Schirber JE, Bayless WR, Chou FC, Johnston DC, Canfield PC, Fisk Z. Pressure dependence of the superconducting transition temperature of superoxygenated La2CuO4+ delta. Phys Rev B Condens Matter 1993; 48:6506-6508. [PMID: 10009201 DOI: 10.1103/physrevb.48.6506] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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