1
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Frachet M, Wang L, Xia W, Guo Y, He M, Maraytta N, Heid R, Haghighirad AA, Merz M, Meingast C, Hardy F. Colossal c-Axis Response and Lack of Rotational Symmetry Breaking within the Kagome Planes of the CsV_{3}Sb_{5} Superconductor. PHYSICAL REVIEW LETTERS 2024; 132:186001. [PMID: 38759199 DOI: 10.1103/physrevlett.132.186001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 03/14/2024] [Accepted: 03/26/2024] [Indexed: 05/19/2024]
Abstract
The kagome materials AV_{3}Sb_{5} (A=K, Rb, Cs) host an intriguing interplay between unconventional superconductivity and charge-density waves. Here, we investigate CsV_{3}Sb_{5} by combining high-resolution thermal-expansion, heat-capacity, and electrical resistance under strain measurements. We directly unveil that the superconducting and charge-ordered states strongly compete, and that this competition is dramatically influenced by tuning the crystallographic c axis. In addition, we report the absence of additional bulk phase transitions within the charge-ordered state, notably associated with rotational symmetry breaking within the kagome planes. This suggests that any breaking of the C_{6} invariance occurs via different stacking of C_{6}-symmetric kagome patterns. Finally, we find that the charge-density-wave phase exhibits an enhanced A_{1g}-symmetric elastoresistance coefficient, whose large increase at low temperature is driven by electronic degrees of freedom.
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Affiliation(s)
- Mehdi Frachet
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - Liran Wang
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - Wei Xia
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
| | - Yanfeng Guo
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
| | - Mingquan He
- Low Temperature Physics Laboratory, College of Physics and Center of Quantum Materials and Devices, Chongqing University, Chongqing 401331, China
| | - Nour Maraytta
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - Rolf Heid
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - Amir-Abbas Haghighirad
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - Michael Merz
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- Karlsruhe Nano Micro Facility (KNMFi), Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Christoph Meingast
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - Frédéric Hardy
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
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2
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Liu C, Bourges P, Sidis Y, Xie T, He G, Bourdarot F, Danilkin S, Ghosh H, Ghosh S, Ma X, Li S, Li Y, Luo H. Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe_{0.96}Ni_{0.04})_{4}As_{4} with Spin-Vortex Crystal Order. PHYSICAL REVIEW LETTERS 2022; 128:137003. [PMID: 35426714 DOI: 10.1103/physrevlett.128.137003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 02/23/2022] [Indexed: 06/14/2023]
Abstract
Spin-orbit coupling (SOC) is a key to understand the magnetically driven superconductivity in iron-based superconductors, where both local and itinerant electrons are present and the orbital angular momentum is not completely quenched. Here, we report a neutron scattering study on the bilayer compound CaK(Fe_{0.96}Ni_{0.04})_{4}As_{4} with superconductivity coexisting with a noncollinear spin-vortex crystal magnetic order that preserves the tetragonal symmetry of the Fe-Fe plane. In the superconducting state, two spin resonance modes with odd and even L symmetries due to the bilayer coupling are found similar to the undoped compound CaKFe_{4}As_{4} but at lower energies. Polarization analysis reveals that the odd mode is c-axis polarized, and the low-energy spin anisotropy can persist to the paramagnetic phase at high temperature, which closely resembles other systems with in-plane collinear and c-axis biaxial magnetic orders. These results provide the missing piece of the puzzle on the SOC effect in iron-pnictide superconductors, and also establish a common picture of c-axis preferred magnetic excitations below T_{c} regardless of the details of magnetic pattern or lattice symmetry.
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Affiliation(s)
- Chang Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Philippe Bourges
- Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - Yvan Sidis
- Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - Tao Xie
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Guanghong He
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | | | - Sergey Danilkin
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization, Lucas Heights NSW-2234, Australia
| | - Haranath Ghosh
- Human Resources Development Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
- Homi Bhabha National Institute, BARC training school complex 2nd floor, Anushakti Nagar, Mumbai 400094, India
| | - Soumyadeep Ghosh
- Human Resources Development Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
- Homi Bhabha National Institute, BARC training school complex 2nd floor, Anushakti Nagar, Mumbai 400094, India
| | - Xiaoyan Ma
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Shiliang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Yuan Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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3
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Reiss P, Graf D, Haghighirad AA, Vojta T, Coldea AI. Signatures of a Quantum Griffiths Phase Close to an Electronic Nematic Quantum Phase Transition. PHYSICAL REVIEW LETTERS 2021; 127:246402. [PMID: 34951778 DOI: 10.1103/physrevlett.127.246402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 10/08/2021] [Indexed: 06/14/2023]
Abstract
In the vicinity of a quantum critical point, quenched disorder can lead to a quantum Griffiths phase, accompanied by an exotic power-law scaling with a continuously varying dynamical exponent that diverges in the zero-temperature limit. Here, we investigate a nematic quantum critical point in the iron-based superconductor FeSe_{0.89}S_{0.11} using applied hydrostatic pressure. We report an unusual crossing of the magnetoresistivity isotherms in the nonsuperconducting normal state that features a continuously varying dynamical exponent over a large temperature range. We interpret our results in terms of a quantum Griffiths phase caused by nematic islands that result from the local distribution of Se and S atoms. At low temperatures, the Griffiths phase is masked by the emergence of a Fermi liquid phase due to a strong nematoelastic coupling and a Lifshitz transition that changes the topology of the Fermi surface.
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Affiliation(s)
- Pascal Reiss
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - David Graf
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
| | - Amir A Haghighirad
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Thomas Vojta
- Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409, USA
| | - Amalia I Coldea
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
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4
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Wu S, Song Y, He Y, Frano A, Yi M, Chen X, Uchiyama H, Alatas A, Said AH, Wang L, Wolf T, Meingast C, Birgeneau RJ. Short-Range Nematic Fluctuations in Sr_{1-x}Na_{x}Fe_{2}As_{2} Superconductors. PHYSICAL REVIEW LETTERS 2021; 126:107001. [PMID: 33784111 DOI: 10.1103/physrevlett.126.107001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 02/02/2021] [Indexed: 06/12/2023]
Abstract
Interactions between nematic fluctuations, magnetic order and superconductivity are central to the physics of iron-based superconductors. Here we report on in-plane transverse acoustic phonons in hole-doped Sr_{1-x}Na_{x}Fe_{2}As_{2} measured via inelastic x-ray scattering, and extract both the nematic susceptibility and the nematic correlation length. By a self-contained method of analysis, for the underdoped (x=0.36) sample, which harbors a magnetically ordered tetragonal phase, we find it hosts a short nematic correlation length ξ∼10 Å and a large nematic susceptibility χ_{nem}. The optimal-doped (x=0.55) sample exhibits weaker phonon softening effects, indicative of both reduced ξ and χ_{nem}. Our results suggest short-range nematic fluctuations may favor superconductivity, placing emphasis on the nematic correlation length for understanding the iron-based superconductors.
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Affiliation(s)
- Shan Wu
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Yu Song
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Yu He
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Alex Frano
- Department of Physics, University of California, San Diego, California 92093, USA
| | - Ming Yi
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Xiang Chen
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Hiroshi Uchiyama
- Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Ahmet Alatas
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Ayman H Said
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Liran Wang
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Thomas Wolf
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Christoph Meingast
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Robert J Birgeneau
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
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5
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Abstract
Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.
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6
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Timmons EI, Tanatar MA, Liu Y, Cho K, Lograsso TA, Kończykowski M, Prozorov R. Mechanical detwinning device for anisotropic resistivity measurements in samples requiring dismounting for particle irradiation. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:073904. [PMID: 32752837 DOI: 10.1063/5.0012053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 06/19/2020] [Indexed: 06/11/2023]
Abstract
Uniaxial stress is used to detwin the samples of orthorhombic iron based superconductors to study their intrinsic electronic anisotropy. Here, we describe the development of a new detwinning setup enabling variable-load stress-detwinning with easy sample mounting/dismounting without the need to re-solder the contacts. It enables the systematic study of the anisotropy evolution as a function of an external parameter when the sample is modified between the measurements. In our case, the external parameter is the dose of 2.5 MeV electron irradiation at low temperature. We illustrate the approach by studying resistivity anisotropy in single crystals of Ba1-xKxFe2As2 at x = 0.25, where the much discussed unusual re-entrance of the tetragonal C4 phase, C4 → C2 → C4, is observed on cooling. With the described technique, we found a significant anisotropy increase in the C2 phase after electron irradiation with a dose of 2.35 C/cm2.
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Affiliation(s)
- E I Timmons
- Ames Laboratory, USDOE, Ames, Iowa 50011, USA
| | - M A Tanatar
- Ames Laboratory, USDOE, Ames, Iowa 50011, USA
| | - Yong Liu
- Ames Laboratory, USDOE, Ames, Iowa 50011, USA
| | - Kyuil Cho
- Ames Laboratory, USDOE, Ames, Iowa 50011, USA
| | | | - M Kończykowski
- Laboratoire des Solides Irradiés, CEA/DRF/lRAMIS, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France
| | - R Prozorov
- Ames Laboratory, USDOE, Ames, Iowa 50011, USA
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7
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Wang L, He M, Hardy F, Aoki D, Willa K, Flouquet J, Meingast C. Electronic Nematicity in URu_{2}Si_{2} Revisited. PHYSICAL REVIEW LETTERS 2020; 124:257601. [PMID: 32639769 DOI: 10.1103/physrevlett.124.257601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
The nature of the hidden-order (HO) state in URu_{2}Si_{2} remains one of the major unsolved issues in heavy-fermion physics. Recently, torque magnetometry, x-ray diffraction, and elastoresistivity data have suggested that the HO phase transition at T_{HO}≈ 17.5 K is driven by electronic nematic effects. Here, we search for thermodynamic signatures of this purported structural instability using anisotropic thermal expansion, Young's modulus, elastoresistivity, and specific-heat measurements. In contrast to the published results, we find no evidence of a rotational symmetry breaking in any of our data. Interestingly, our elastoresistivity measurements, which are in full agreement with published results, exhibit a Curie-Weiss divergence, which we however attribute to a volume and not to a symmetry-breaking effect. Finally, clear evidence for thermal fluctuations is observed in our heat-capacity data, from which we estimate the HO correlation length.
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Affiliation(s)
- Liran Wang
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Mingquan He
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Frédéric Hardy
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Dai Aoki
- Université Grenoble Alpes, CEA, PHELIQS, 38000 Grenoble, France
- Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
| | - Kristin Willa
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | | | - Christoph Meingast
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
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8
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Han TT, Chen L, Cai C, Wang YD, Wang ZG, Xin ZM, Zhang Y. Isostructural Spin-Density-Wave and Superconducting Gap Anisotropies in Iron-Arsenide Superconductors. PHYSICAL REVIEW LETTERS 2020; 124:247002. [PMID: 32639832 DOI: 10.1103/physrevlett.124.247002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
When passing through a phase transition, electronic system saves energy by opening energy gaps at the Fermi level. Delineating the energy gap anisotropy provides insights into the origin of the interactions that drive the phase transition. Here, we report the angle-resolved photoemission spectroscopy (ARPES) study on the detailed gap anisotropies in both the tetragonal magnetic and superconducting phases in Sr_{1-x}Na_{x}Fe_{2}As_{2}. First, we found that the spin-density-wave (SDW) gap is strongly anisotropic in the tetragonal magnetic phase. The gap magnitude correlates with the orbital character of Fermi surface closely. Second, we found that the SDW gap anisotropy is isostructural to the superconducting gap anisotropy regarding to the angular dependence, gap minima locations, and relative gap magnitudes. Our results indicate that the superconducting pairing interaction and magnetic interaction share the same origin. The intraorbital scattering plays an important role in constructing these interactions resulting in the orbital-selective magnetism and superconductivity in iron-based superconductors.
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Affiliation(s)
- T T Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - L Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - C Cai
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y D Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z G Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Z M Xin
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Y Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
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9
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Gati E, Böhmer AE, Bud'ko SL, Canfield PC. Bulk Superconductivity and Role of Fluctuations in the Iron-Based Superconductor FeSe at High Pressures. PHYSICAL REVIEW LETTERS 2019; 123:167002. [PMID: 31702365 DOI: 10.1103/physrevlett.123.167002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Indexed: 06/10/2023]
Abstract
The iron-based superconductor FeSe offers a unique possibility to study the interplay of superconductivity with purely nematic as well magnetic-nematic order by pressure (p) tuning. By measuring specific heat under p up to 2.36 GPa, we study the multiple phases in FeSe using a thermodynamic probe. We conclude that superconductivity is bulk across the entire p range and competes with magnetism. In addition, whenever magnetism is present, fluctuations exist over a wide temperature range above both the bulk superconducting and the magnetic transitions. Whereas the magnetic fluctuations are likely temporal, the superconducting fluctuations may be either temporal or spatial. These observations highlight similarities between FeSe and underdoped cuprate superconductors.
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Affiliation(s)
- Elena Gati
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Anna E Böhmer
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Sergey L Bud'ko
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Paul C Canfield
- Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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10
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Xu B, Cappelluti E, Benfatto L, Mallett BPP, Marsik P, Sheveleva E, Lyzwa F, Wolf T, Yang R, Qiu XG, Dai YM, Wen HH, Lobo RPSM, Bernhard C. Scaling of the Fano Effect of the In-Plane Fe-As Phonon and the Superconducting Critical Temperature in Ba_{1-x}K_{x}Fe_{2}As_{2}. PHYSICAL REVIEW LETTERS 2019; 122:217002. [PMID: 31283343 DOI: 10.1103/physrevlett.122.217002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Indexed: 06/09/2023]
Abstract
By means of infrared spectroscopy, we determine the temperature-doping phase diagram of the Fano effect for the in-plane Fe-As stretching mode in Ba_{1-x}K_{x}Fe_{2}As_{2}. The Fano parameter 1/q^{2}, which is a measure of the phonon coupling to the electronic particle-hole continuum, shows a remarkable sensitivity to the magnetic and structural orderings at low temperatures. Most strikingly, at elevated temperatures in the paramagnetic tetragonal state we observe a linear correlation between 1/q^{2} and the superconducting critical temperature T_{c}. Based on theoretical calculations and symmetry considerations, we identify the relevant interband transitions that are coupled to the Fe-As mode. In particular, we show that a sizable xy orbital component at the Fermi level is fundamental for the Fano effect and, thus, possibly also for the superconducting pairing.
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Affiliation(s)
- B Xu
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - E Cappelluti
- Istituto di Struttura della Materia, CNR, 34149 Trieste, Italy
| | - L Benfatto
- ISC-CNR and Department of Physics, Sapienza University of Rome, P. le A. Moro 5, 00185 Rome, Italy
| | - B P P Mallett
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
- The Photon Factory, Department of Physics, University of Auckland, 38 Princes Street, Auckland 1010, New Zealand
| | - P Marsik
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - E Sheveleva
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - F Lyzwa
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
| | - Th Wolf
- Institute of Solid State Physics, Karlsruhe Institute of Technology, Postfach 3640, Karlsruhe 76021, Germany
| | - R Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - X G Qiu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Y M Dai
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - H H Wen
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - R P S M Lobo
- LPEM, ESPCI Paris, PSL University, CNRS, F-75005 Paris, France
- Sorbonne Université, CNRS, LPEM, F-75005 Paris, France
| | - C Bernhard
- University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, CH-1700 Fribourg, Switzerland
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11
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Carpenter MA, Evans DM, Schiemer JA, Wolf T, Adelmann P, Böhmer AE, Meingast C, Dutton SE, Mukherjee P, Howard CJ. Ferroelasticity, anelasticity and magnetoelastic relaxation in Co-doped iron pnictide: Ba(Fe 0.957Co 0.043) 2As 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:155401. [PMID: 30641499 DOI: 10.1088/1361-648x/aafe29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The hypothesis that strain has a permeating influence on ferroelastic, magnetic and superconducting transitions in 122 iron pnictides has been tested by investigating variations of the elastic and anelastic properties of a single crystal of Ba(Fe0.957Co0.043)2As2 by resonant ultrasound spectroscopy as a function of temperature and externally applied magnetic field. Non-linear softening and stiffening of C 66 in the stability fields of both the tetragonal and orthorhombic structures has been found to conform quantitatively to the Landau expansion for a pseudoproper ferroelastic transition which is second order in character. The only exception is that the transition occurs at a temperature (T S ≈ 69 K) ~10 K above the temperature at which C 66 would extrapolate to zero ([Formula: see text] ≈ 59 K). An absence of anomalies associated with antiferromagnetic ordering below T N ≈ 60 K implies that coupling of the magnetic order parameter with shear strain is weak. It is concluded that linear-quadratic coupling between the structural/electronic and antiferromagnetic order parameters is suppressed due to the effects of local heterogeneous strain fields arising from the substitution of Fe by Co. An acoustic loss peak at ~50-55 K is attributed to the influence of mobile ferroelastic twin walls that become pinned by a thermally activated process involving polaronic defects. Softening of C 66 by up to ~6% below the normal-superconducting transition at T c ≈ 13 K demonstrates an effective coupling of the shear strain with the order parameter for the superconducting transition which arises indirectly as a consequence of unfavourable coupling of the superconducting order parameter with the ferroelastic order parameter. Ba(Fe0.957Co0.043)2As2 is representative of 122 pnictides as forming a class of multiferroic superconductors in which elastic strain relaxations underpin almost all aspects of coupling between the structural, magnetic and superconducting order parameters and of dynamic properties of the transformation microstructures they contain.
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Affiliation(s)
- M A Carpenter
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
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12
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Trainer C, Yim CM, Heil C, Giustino F, Croitori D, Tsurkan V, Loidl A, Rodriguez EE, Stock C, Wahl P. Manipulating surface magnetic order in iron telluride. SCIENCE ADVANCES 2019; 5:eaav3478. [PMID: 30838332 PMCID: PMC6397027 DOI: 10.1126/sciadv.aav3478] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/22/2019] [Indexed: 06/09/2023]
Abstract
Control of emergent magnetic orders in correlated electron materials promises new opportunities for applications in spintronics. For their technological exploitation, it is important to understand the role of surfaces and interfaces to other materials and their impact on the emergent magnetic orders. Here, we demonstrate for iron telluride, the nonsuperconducting parent compound of the iron chalcogenide superconductors, determination and manipulation of the surface magnetic structure by low-temperature spin-polarized scanning tunneling microscopy. Iron telluride exhibits a complex structural and magnetic phase diagram as a function of interstitial iron concentration. Several theories have been put forward to explain the different magnetic orders observed in the phase diagram, which ascribe a dominant role either to interactions mediated by itinerant electrons or to local moment interactions. Through the controlled removal of surface excess iron, we can separate the influence of the excess iron from that of the change in the lattice structure.
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Affiliation(s)
- Christopher Trainer
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Chi M. Yim
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Christoph Heil
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
- Institute of Theoretical and Computational Physics, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
| | - Feliciano Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
| | - Dorina Croitori
- Center for Electronic Correlations and Magnetism, Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova
| | - Vladimir Tsurkan
- Center for Electronic Correlations and Magnetism, Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova
| | - Alois Loidl
- Center for Electronic Correlations and Magnetism, Experimental Physics V, University of Augsburg, D-86159 Augsburg, Germany
| | - Efrain E. Rodriguez
- Department of Chemistry of Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Chris Stock
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, UK
| | - Peter Wahl
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
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13
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Guo J, Yue L, Iida K, Kamazawa K, Chen L, Han T, Zhang Y, Li Y. Preferred Magnetic Excitations in the Iron-Based Sr_{1-x}Na_{x}Fe_{2}As_{2} Superconductor. PHYSICAL REVIEW LETTERS 2019; 122:017001. [PMID: 31012685 DOI: 10.1103/physrevlett.122.017001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 10/16/2018] [Indexed: 06/09/2023]
Abstract
With spin-orbit coupling, both local-moment magnetism and itinerant electrons are expected to behave anisotropically in spin space, but such effects' influence on the formation of unconventional superconductivity has been hitherto unexplored. Here, in an iron-based superconductor, Sr_{1-x}Na_{x}Fe_{2}As_{2}, we report spectroscopic evidence that itinerant electrons "prefer" to be assisted by c-axis polarized magnetic excitations in their formation of superconducting Cooper pairs, against the polarization of the local-moment excitations. Our result naturally explains why the superconductivity competes strongly with the tetragonal magnetic phase in this material, and provides a fresh view on how to make a good superconductor out of a magnetic "Hund's metal."
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Affiliation(s)
- Jianqing Guo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Li Yue
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Kazuki Iida
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Kazuya Kamazawa
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Lei Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Tingting Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Yan Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Yuan Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
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14
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Yi M, Frano A, Lu DH, He Y, Wang M, Frandsen BA, Kemper AF, Yu R, Si Q, Wang L, He M, Hardy F, Schweiss P, Adelmann P, Wolf T, Hashimoto M, Mo SK, Hussain Z, Le Tacon M, Böhmer AE, Lee DH, Shen ZX, Meingast C, Birgeneau RJ. Spectral Evidence for Emergent Order in Ba_{1-x}Na_{x}Fe_{2}As_{2}. PHYSICAL REVIEW LETTERS 2018; 121:127001. [PMID: 30296157 DOI: 10.1103/physrevlett.121.127001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Revised: 07/05/2018] [Indexed: 06/08/2023]
Abstract
We report an angle-resolved photoemission spectroscopy study of the iron-based superconductor family, Ba_{1-x}Na_{x}Fe_{2}As_{2}. This system harbors the recently discovered double-Q magnetic order appearing in a reentrant C_{4} phase deep within the underdoped regime of the phase diagram that is otherwise dominated by the coupled nematic phase and collinear antiferromagnetic order. From a detailed temperature-dependence study, we identify the electronic response to the nematic phase in an orbital-dependent band shift that strictly follows the rotational symmetry of the lattice and disappears when the system restores C_{4} symmetry in the low temperature phase. In addition, we report the observation of a distinct electronic reconstruction that cannot be explained by the known electronic orders in the system.
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Affiliation(s)
- M Yi
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - A Frano
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - D H Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Y He
- Stanford Institute of Materials and Energy Sciences, Stanford University, Stanford, California 94305, USA
- Departments of Physics and Applied Physics, and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - Meng Wang
- School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - B A Frandsen
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A F Kemper
- Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - R Yu
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - Q Si
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - L Wang
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
- Kirchhoff-Institute for Physics, Universitt Heidelberg, D-69120 Heidelberg, Germany
| | - M He
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - F Hardy
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - P Schweiss
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - P Adelmann
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - T Wolf
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - M Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Z Hussain
- Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - M Le Tacon
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - A E Böhmer
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - D-H Lee
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Z-X Shen
- Stanford Institute of Materials and Energy Sciences, Stanford University, Stanford, California 94305, USA
- Departments of Physics and Applied Physics, and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - C Meingast
- Institute for Solid State Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - R J Birgeneau
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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15
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Christensen MH, Orth PP, Andersen BM, Fernandes RM. Emergent Magnetic Degeneracy in Iron Pnictides due to the Interplay between Spin-Orbit Coupling and Quantum Fluctuations. PHYSICAL REVIEW LETTERS 2018; 121:057001. [PMID: 30118255 DOI: 10.1103/physrevlett.121.057001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Indexed: 06/08/2023]
Abstract
Recent experiments in iron pnictide superconductors reveal that, as the putative magnetic quantum critical point is approached, different types of magnetic order coexist over a narrow region of the phase diagram. Although these magnetic configurations share the same wave vectors, they break distinct symmetries of the lattice. Importantly, the highest superconducting transition temperature takes place close to this proliferation of near-degenerate magnetic states. In this Letter, we employ a renormalization group calculation to show that such a behavior naturally arises due to the effects of spin-orbit coupling on the quantum magnetic fluctuations. Formally, the enhanced magnetic degeneracy near the quantum critical point is manifested as a stable Gaussian fixed point with a large basin of attraction. Implications of our findings to the superconductivity of the iron pnictides are also discussed.
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Affiliation(s)
- Morten H Christensen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Peter P Orth
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
- Ames Laboratory, U.S. DOE, Iowa State University, Ames, Iowa 50011, USA
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100, Denmark
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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16
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Scherer DD, Andersen BM. Spin-Orbit Coupling and Magnetic Anisotropy in Iron-Based Superconductors. PHYSICAL REVIEW LETTERS 2018; 121:037205. [PMID: 30085777 DOI: 10.1103/physrevlett.121.037205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Indexed: 06/08/2023]
Abstract
We determine theoretically the effect of spin-orbit coupling on the magnetic excitation spectrum of itinerant multiorbital systems, with specific application to iron-based superconductors. Our microscopic model includes a realistic ten-band kinetic Hamiltonian, atomic spin-orbit coupling, and multiorbital Hubbard interactions. Our results highlight the remarkable variability of the resulting magnetic anisotropy despite constant spin-orbit coupling. At the same time, the magnetic anisotropy exhibits robust universal behavior upon changes in the band structure corresponding to different materials of iron-based superconductors. A natural explanation of the observed universality emerges when considering optimal nesting as a resonance phenomenon. Our theory is also of relevance to other itinerant systems with spin-orbit coupling and nesting tendencies in the band structure.
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Affiliation(s)
- Daniel D Scherer
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
| | - Brian M Andersen
- Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
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17
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Sangeetha NS, Smetana V, Mudring AV, Johnston DC. Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca_{1-x}Sr_{x}Co_{2-y}As_{2}. PHYSICAL REVIEW LETTERS 2017; 119:257203. [PMID: 29303352 DOI: 10.1103/physrevlett.119.257203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Indexed: 06/07/2023]
Abstract
The inference of Ying et al. [Europhys. Lett. 104, 67005 (2013)EULEEJ0295-507510.1209/0295-5075/104/67005] of a composition-induced change from c-axis ordered-moment alignment in a collinear A-type antiferromagnetic (AFM) structure at small x to ab-plane alignment in an unknown AFM structure at larger x in Ca_{1-x}Sr_{x}Co_{2-y}As_{2} with the body-centered tetragonal ThCr_{2}Si_{2} structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2≲x≲0.3 between these two phases. In this region the magnetic susceptibility vs temperature χ_{ab}(T) measured with magnetic fields H applied in the ab plane exhibit typical AFM behaviors with cusps at the Néel temperatures of ∼ 65 K, whereas χ_{c}(T) and the low-temperature isothermal magnetization M_{c}(H) with H aligned along the c axis exhibit extremely soft ferromagneticlike behaviors.
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Affiliation(s)
- N S Sangeetha
- Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
| | - V Smetana
- Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
- Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - A-V Mudring
- Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
- Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - D C Johnston
- Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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18
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Frustration-driven C 4 symmetric order in a naturally-heterostructured superconductor Sr 2VO 3FeAs. Nat Commun 2017; 8:2167. [PMID: 29255140 PMCID: PMC5735138 DOI: 10.1038/s41467-017-02327-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 11/15/2017] [Indexed: 11/08/2022] Open
Abstract
A subtle balance between competing interactions in iron-based superconductors (FeSCs) can be tipped by additional interfacial interactions in a heterostructure, often inducing exotic phases with unprecedented properties. Particularly when the proximity-coupled layer is magnetically active, rich phase diagrams are expected in FeSCs, but this has not been explored yet. Here, using high-accuracy 75As and 51V nuclear magnetic resonance measurements, we investigate an electronic phase that emerges in the FeAs layer below T 0 ~ 155 K of Sr2VO3FeAs, a naturally assembled heterostructure of an FeSC and a Mott-insulating vanadium oxide. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order in the FeAs layers, without either static magnetism or broken C 4 symmetry, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling stabilizes a hidden order in FeSCs, which may also apply to other strongly correlated heterostructures.
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19
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Choi S, Choi HJ, Ok JM, Lee Y, Jang WJ, Lee AT, Kuk Y, Lee S, Heinrich AJ, Cheong SW, Bang Y, Johnston S, Kim JS, Lee J. Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor. PHYSICAL REVIEW LETTERS 2017; 119:227001. [PMID: 29286823 DOI: 10.1103/physrevlett.119.227001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Indexed: 06/07/2023]
Abstract
We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C_{4} (2×2) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C_{4} state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.
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Affiliation(s)
- Seokhwan Choi
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Hyoung Joon Choi
- Department of Physics and Center for Computational Studies of Advanced Electronic Material Properties, Yonsei University, Seoul 03722, Korea
| | - Jong Mok Ok
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
| | - Yeonghoon Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Won-Jun Jang
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34051, Korea
| | - Alex Taekyung Lee
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - Young Kuk
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - SungBin Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Andreas J Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Korea
- Physics Department, Ewha Womans University, Seoul 03760, Korea
| | - Sang-Wook Cheong
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Yunkyu Bang
- Department of Physics, Chonnam National University, Gwangju 61186, Korea
| | - Steven Johnston
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - Jun Sung Kim
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
| | - Jhinhwan Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
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20
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Frandsen BA, Taddei KM, Yi M, Frano A, Guguchia Z, Yu R, Si Q, Bugaris DE, Stadel R, Osborn R, Rosenkranz S, Chmaissem O, Birgeneau RJ. Local Orthorhombicity in the Magnetic C_{4} Phase of the Hole-Doped Iron-Arsenide Superconductor Sr_{1-x}Na_{x}Fe_{2}As_{2}. PHYSICAL REVIEW LETTERS 2017; 119:187001. [PMID: 29219610 DOI: 10.1103/physrevlett.119.187001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Indexed: 06/07/2023]
Abstract
We report on temperature-dependent pair distribution function measurements of Sr_{1-x}Na_{x}Fe_{2}As_{2}, an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C_{4} phase. Quantitative refinements indicate that the instantaneous local structure in the C_{4} phase comprises fluctuating orthorhombic regions with a length scale of ∼2 nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. These results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C_{4} phase and the neighboring C_{2} and superconducting phases.
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Affiliation(s)
- Benjamin A Frandsen
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Keith M Taddei
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Ming Yi
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Alex Frano
- Department of Physics, University of California, Berkeley, California 94720, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Zurab Guguchia
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - Rong Yu
- Department of Physics, Renmin University of China, Beijing 100872, China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qimiao Si
- Department of Physics and Astronomy and Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Daniel E Bugaris
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Ryan Stadel
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Physics, Northern Illinois University, DeKalb, Illinois 60439, USA
| | - Raymond Osborn
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Stephan Rosenkranz
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Omar Chmaissem
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Physics, Northern Illinois University, DeKalb, Illinois 60439, USA
| | - Robert J Birgeneau
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, University of California, Berkeley, California 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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21
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Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained BaFe 2As 2. Nat Commun 2017; 8:504. [PMID: 28894127 PMCID: PMC5593886 DOI: 10.1038/s41467-017-00712-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 07/21/2017] [Indexed: 11/08/2022] Open
Abstract
High-temperature superconductivity in the Fe-based materials emerges when the antiferromagnetism of the parent compounds is suppressed by either doping or pressure. Closely connected to the antiferromagnetic state are entangled orbital, lattice, and nematic degrees of freedom, and one of the major goals in this field has been to determine the hierarchy of these interactions. Here we present the direct measurements and the calculations of the in-plane uniform magnetic susceptibility anisotropy of BaFe2As2, which help in determining the above hierarchy. The magnetization measurements are made possible by utilizing a simple method for applying a large symmetry-breaking strain, based on differential thermal expansion. In strong contrast to the large resistivity anisotropy above the antiferromagnetic transition at T N, the anisotropy of the in-plane magnetic susceptibility develops largely below T N. Our results imply that lattice and orbital degrees of freedom play a subdominant role in these materials.Interplay between lattice, orbital, magnetic and nematic degrees of freedom is crucial for the superconductivity in Fe-based materials. Here, the authors demonstrate the subdominant roles of pure lattice distortions and/or orbital ordering in BaFe2As2 by characterizing the in-plane magnetic susceptibility anisotropy.
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22
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Böhmer AE, Sapkota A, Kreyssig A, Bud'ko SL, Drachuck G, Saunders SM, Goldman AI, Canfield PC. Effect of Biaxial Strain on the Phase Transitions of Ca(Fe_{1-x}Co_{x})_{2}As_{2}. PHYSICAL REVIEW LETTERS 2017; 118:107002. [PMID: 28339236 DOI: 10.1103/physrevlett.118.107002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Indexed: 06/06/2023]
Abstract
We study the effect of applied strain as a physical control parameter for the phase transitions of Ca(Fe_{1-x}Co_{x})_{2}As_{2} using resistivity, magnetization, x-ray diffraction, and ^{57}Fe Mössbauer spectroscopy. Biaxial strain, namely, compression of the basal plane of the tetragonal unit cell, is created through firm bonding of samples to a rigid substrate via differential thermal expansion. This strain is shown to induce a magnetostructural phase transition in originally paramagnetic samples, and superconductivity in previously nonsuperconducting ones. The magnetostructural transition is gradual as a consequence of using strain instead of pressure or stress as a tuning parameter.
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Affiliation(s)
- A E Böhmer
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
| | - A Sapkota
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - A Kreyssig
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - S L Bud'ko
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - G Drachuck
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - S M Saunders
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - A I Goldman
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - P C Canfield
- Ames Laboratory, US DOE, Ames, Iowa 50011, USA
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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23
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Scanning tunnelling spectroscopy as a probe of multi-Q magnetic states of itinerant magnets. Nat Commun 2017; 8:14317. [PMID: 28176779 PMCID: PMC5309833 DOI: 10.1038/ncomms14317] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 12/16/2016] [Indexed: 11/14/2022] Open
Abstract
The combination of electronic correlations and Fermi surfaces with multiple nesting vectors can lead to the appearance of complex multi-Q magnetic ground states, hosting unusual states such as chiral density waves and quantum Hall insulators. Distinguishing single-Q and multi-Q magnetic phases is however a notoriously difficult experimental problem. Here we propose theoretically that the local density of states (LDOS) near a magnetic impurity, whose orientation may be controlled by an external magnetic field, can be used to map out the detailed magnetic configuration of an itinerant system and distinguish unambiguously between single-Q and multi-Q phases. We demonstrate this concept by computing and contrasting the LDOS near a magnetic impurity embedded in three different magnetic ground states relevant to iron-based superconductors—one single-Q and two double-Q phases. Our results open a promising avenue to investigate the complex magnetic configurations in itinerant systems via standard scanning tunnelling spectroscopy, without requiring spin-resolved capability. It remains difficult to distinguish single-Q and multi-Q magnetic states experimentally. Here, Gastiasoro et al. show that the magnetic configuration of an itinerant system can be mapped out to the local density of states near a magnetic impurity, distinguishing unambiguously between single-Q and multi-Q phases.
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Fernandes RM, Chubukov AV. Low-energy microscopic models for iron-based superconductors: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:014503. [PMID: 27876709 DOI: 10.1088/1361-6633/80/1/014503] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The development of sensible microscopic models is essential to elucidate the normal-state and superconducting properties of the iron-based superconductors. Because these materials are mostly metallic, a good starting point is an effective low-energy model that captures the electronic states near the Fermi level and their interactions. However, in contrast to cuprates, iron-based high-T c compounds are multi-orbital systems with Hubbard and Hund interactions, resulting in a rather involved 10-orbital lattice model. Here we review different minimal models that have been proposed to unveil the universal features of these systems. We first review minimal models defined solely in the orbital basis, which focus on a particular subspace of orbitals, or solely in the band basis, which rely only on the geometry of the Fermi surface. The former, while providing important qualitative insight into the role of the orbital degrees of freedom, do not distinguish between high-energy and low-energy sectors and, for this reason, generally do not go beyond mean-field. The latter allow one to go beyond mean-field and investigate the interplay between superconducting and magnetic orders as well as Ising-nematic order. However, they cannot capture orbital-dependent features like spontaneous orbital order. We then review recent proposals for a minimal model that operates in the band basis but fully incorporates the orbital composition and symmetries of the low-energy excitations. We discuss the results of the renormalization group study of such a model, particularly of the interplay between superconductivity, magnetism, and spontaneous orbital order, and compare theoretical predictions with experiments on iron pnictides and chalcogenides. We also discuss the impact of the glide-plane symmetry on the low-energy models, highlighting the key role played by the spin-orbit coupling.
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Polarized Light Microscopy Study on the Reentrant Phase Transition in a (Ba1 – xKx)Fe2As2 Single Crystal with x = 0.24. CRYSTALS 2016. [DOI: 10.3390/cryst6110142] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Eilers F, Grube K, Zocco DA, Wolf T, Merz M, Schweiss P, Heid R, Eder R, Yu R, Zhu JX, Si Q, Shibauchi T, Löhneysen HV. Strain-Driven Approach to Quantum Criticality in AFe_{2}As_{2} with A=K, Rb, and Cs. PHYSICAL REVIEW LETTERS 2016; 116:237003. [PMID: 27341252 DOI: 10.1103/physrevlett.116.237003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 06/06/2023]
Abstract
The iron-based superconductors AFe_{2}As_{2} with A=K, Rb, Cs exhibit large Sommerfeld coefficients approaching those of heavy-fermion systems. We have investigated the magnetostriction and thermal expansion of this series to shed light on this unusual behavior. Quantum oscillations of the magnetostriction allow identifying the band-specific quasiparticle masses which by far exceed the band-structure derived masses. The divergence of the Grüneisen ratio derived from thermal expansion indicates that with increasing volume along the series a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to weaken the superconducting state.
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Affiliation(s)
- Felix Eilers
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Kai Grube
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Diego A Zocco
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Thomas Wolf
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Michael Merz
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Peter Schweiss
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Rolf Heid
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Robert Eder
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
| | - Rong Yu
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - Jian-Xin Zhu
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Qimiao Si
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Takasada Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
- Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Hilbert V Löhneysen
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany
- Physikalisches Institut, Karlsruher Institut für Technologie, 76049 Karlsruhe, Germany
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