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Xu Y, Das L, Ma JZ, Yi CJ, Nie SM, Shi YG, Tiwari A, Tsirkin SS, Neupert T, Medarde M, Shi M, Chang J, Shang T. Unconventional Transverse Transport above and below the Magnetic Transition Temperature in Weyl Semimetal EuCd_{2}As_{2}. Phys Rev Lett 2021; 126:076602. [PMID: 33666464 DOI: 10.1103/physrevlett.126.076602] [Citation(s) in RCA: 2] [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: 08/12/2020] [Revised: 11/13/2020] [Accepted: 01/25/2021] [Indexed: 06/12/2023]
Abstract
As exemplified by the growing interest in the quantum anomalous Hall effect, the research on topology as an organizing principle of quantum matter is greatly enriched from the interplay with magnetism. In this vein, we present a combined electrical and thermoelectrical transport study on the magnetic Weyl semimetal EuCd_{2}As_{2}. Unconventional contribution to the anomalous Hall and anomalous Nernst effects were observed both above and below the magnetic transition temperature of EuCd_{2}As_{2}, indicating the existence of significant Berry curvature. EuCd_{2}As_{2} represents a rare case in which this unconventional transverse transport emerges both above and below the magnetic transition temperature in the same material. The transport properties evolve with temperature and field in the antiferromagnetic phase in a different manner than in the paramagnetic phase, suggesting different mechanisms to their origin. Our results indicate EuCd_{2}As_{2} is a fertile playground for investigating the interplay between magnetism and topology, and potentially a plethora of topologically nontrivial phases rooted in this interplay.
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Affiliation(s)
- Y Xu
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - L Das
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - J Z Ma
- Department of Physics, City University of Hong Kong, Kowloon, Hong Kong
- Swiss Light Source, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - C J Yi
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - S M Nie
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94035, USA
| | - Y G Shi
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - A Tiwari
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - S S Tsirkin
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - T Neupert
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - M Medarde
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - J Chang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - T Shang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China
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Sun JP, Jiao YY, Yi CJ, Dissanayake SE, Matsuda M, Uwatoko Y, Shi YG, Li YQ, Fang Z, Cheng JG. Magnetic-Competition-Induced Colossal Magnetoresistance in n-Type HgCr_{2}Se_{4} under High Pressure. Phys Rev Lett 2019; 123:047201. [PMID: 31491259 DOI: 10.1103/physrevlett.123.047201] [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: 03/25/2019] [Indexed: 06/10/2023]
Abstract
The n-type HgCr_{2}Se_{4} exhibits a sharp semiconductor-to-metal transition (SMT) in resistivity accompanying the ferromagnetic order at T_{C}=106 K. Here, we investigate the effects of pressure and magnetic field on the concomitant SMT and ferromagnetic order by measuring resistivity, dc and ac magnetic susceptibility, as well as single-crystal neutron diffraction under various pressures up to 8 GPa and magnetic fields up to 8 T. Our results demonstrate that the ferromagnetic metallic ground state of n-type HgCr_{2}Se_{4} is destabilized and gradually replaced by an antiferromagnetic, most likely a spiral magnetic, and insulating ground state upon the application of high pressure. On the other hand, the application of external magnetic fields can restore the ferromagnetic metallic state again at high pressures, resulting in a colossal magnetoresistance (CMR) as high as ∼ 3×10^{11}% under 5 T and 2 K at 4 GPa. The present study demonstrates that n-type HgCr_{2}Se_{4} is located at a peculiar critical point where the balance of competition between ferromagnetic and antiferromagnetic interactions can be easily tipped by external stimuli, providing a new platform for achieving CMR in a single-valent system.
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Affiliation(s)
- J P Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Y Y Jiao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Faculty of Science, Wuhan University of Science and Technology, Wuhan, Hubei 430065, China
| | - C J Yi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - S E Dissanayake
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Physics, Duke University, Durham, North Carolina 27708, USA
| | - M Matsuda
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Uwatoko
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Y G Shi
- Beijing National Laboratory for Condensed Matter Physics and 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
| | - Y Q Li
- Beijing National Laboratory for Condensed Matter Physics and 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
| | - Z Fang
- Beijing National Laboratory for Condensed Matter Physics and 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
| | - J-G Cheng
- Beijing National Laboratory for Condensed Matter Physics and 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
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Luo J, Yang J, Zhou R, Mu QG, Liu T, Ren ZA, Yi CJ, Shi YG, Zheng GQ. Tuning the Distance to a Possible Ferromagnetic Quantum Critical Point in A_{2}Cr_{3}As_{3}. Phys Rev Lett 2019; 123:047001. [PMID: 31491262 DOI: 10.1103/physrevlett.123.047001] [Citation(s) in RCA: 3] [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: 03/12/2019] [Indexed: 06/10/2023]
Abstract
Although superconductivity in the vicinity of an antiferromagnetic (AFM) instability has been extensively explored in the last three decades or so, superconductivity in compounds with a background of ferromagnetic (FM) spin fluctuations is still rare. We report ^{75}As nuclear quadrupole resonance measurements on the A_{2}Cr_{3}As_{3} family, which is the first group of Cr-based superconductors at ambient pressure, with A being alkali elements. From the temperature dependence of the spin-lattice relaxation rate (1/T_{1}), we find that by changing A in the order of A=Na, Na_{0.75}K_{0.25}, K, and Rb, the system is tuned to approach a possible FM quantum critical point (QCP). This may be ascribed to the Cr2-As2-Cr2 bond angle that decreases towards 90°, which enhances the FM interaction via the Cr2-As2-Cr2 path. Upon moving away from the QCP, the superconducting transition temperature T_{sc} increases progressively up to 8.0 K in Na_{2}Cr_{3}As_{3}, which is in sharp contrast to the AFM case where T_{sc} usually shows a maximum around a QCP. The 1/T_{1} decreases rapidly below T_{sc} with no Hebel-Slichter peak, and ubiquitously follows a T^{5} variation below a characteristic temperature T^{*}≈0.6 T_{sc}, which indicates the existence of point nodes in the superconducting gap function commonly in the family. These results suggest that the A_{2}Cr_{3}As_{3} family is a possible solid-state analog of superfluid ^{3}He.
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Affiliation(s)
- J Luo
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - J Yang
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - R Zhou
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - Q G Mu
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - T Liu
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Zhi-An Ren
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - C J Yi
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Y G Shi
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - Guo-Qing Zheng
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
- Department of Physics, Okayama University, Okayama 700-8530, Japan
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Ma JZ, Nie SM, Yi CJ, Jandke J, Shang T, Yao MY, Naamneh M, Yan LQ, Sun Y, Chikina A, Strocov VN, Medarde M, Song M, Xiong YM, Xu G, Wulfhekel W, Mesot J, Reticcioli M, Franchini C, Mudry C, Müller M, Shi YG, Qian T, Ding H, Shi M. Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd 2As 2. Sci Adv 2019; 5:eaaw4718. [PMID: 31309151 PMCID: PMC6625818 DOI: 10.1126/sciadv.aaw4718] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 06/10/2019] [Indexed: 05/22/2023]
Abstract
Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd2As2. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi-long-range ferromagnetic fluctuations. Moreover, the spin-nondegenerate band structure harbors a pair of ideal Weyl nodes near the Fermi level. Hence, we show that long-range magnetic order and the spontaneous breaking of time-reversal symmetry are not essential requirements for WSM states in centrosymmetric systems and that WSM states can emerge in a wider range of condensed matter systems than previously thought.
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Affiliation(s)
- J.-Z. Ma
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15 Lausanne, Switzerland
| | - S. M. Nie
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
| | - C. J. Yi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China
| | - J. Jandke
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - T. Shang
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15 Lausanne, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Y. Yao
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Naamneh
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - L. Q. Yan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Y. Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - A. Chikina
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - V. N. Strocov
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Medarde
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Song
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Y.-M. Xiong
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - G. Xu
- Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - W. Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - J. Mesot
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15 Lausanne, Switzerland
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - M. Reticcioli
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Vienna, Austria
| | - C. Franchini
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Vienna, Austria
- Dipartimento di Fisica e Astronomia, Università di Bologna, 40127 Bologna, Italy
| | - C. Mudry
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Physics, Ecole Polytechnique Federale de Lausanne, CH1015 Lausanne, Switzerland
| | - M. Müller
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Y. G. Shi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - T. Qian
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - H. Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - M. Shi
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
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Sun JP, Jiao YY, Yang CL, Wu W, Yi CJ, Wang BS, Shi YG, Luo JL, Uwatoko Y, Cheng JG. Effect of hydrostatic pressure on the superconducting properties of quasi-1D superconductor K 2Cr 3As 3. J Phys Condens Matter 2017; 29:455603. [PMID: 29049031 DOI: 10.1088/1361-648x/aa8c94] [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
K2Cr3As3 is a newly discovered quasi-1D superconductor with a T c = 6.1 K and an upper critical field µ 0 H c2(0) ≈ 40 T three times larger than the Pauli paramagnetic limit µ 0 H p that is suggestive of a spin-triplet Cooper pairing. In this paper, we have investigated the effects of hydrostatic pressure on its T c and µ 0 H c2 by measuring the ac magnetic susceptibility χ'(T) under magnetic fields at various hydrostatic pressures up to 7.5 GPa. The major findings include: (1) T c is suppressed gradually to below 2 K at 7.5 GPa; (2) the estimated µ 0 H c2(0) decreases dramatically to below µ 0 H p above ~2 GPa and becomes slight lower than the orbital limiting field [Formula: see text] estimated from the initial slope of upper critical field via [Formula: see text] = -0.73T cdH c2/[Formula: see text] in the clean limit; (3) the estimated Maki parameter α = √2[Formula: see text]/H p drops from 4 at ambient pressure to well below 1 at P > 2 GPa, suggesting the crossover from Pauli paramagnetic limiting to orbital limiting in the pair breaking process upon increasing pressure. These observations suggested that the application of hydrostatic pressure could drive K2Cr3As3 away from the ferromagnetic instability and lead to a breakdown of the spin-triplet pairing channel. We have also made a side-by-side comparison and discussed the distinct effects of chemical and physical pressures on the superconducting properties of K2Cr3As3.
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Affiliation(s)
- J P Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China. School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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Abstract
BACKGROUND AND PURPOSE Ginkgo biloba leaf extract (GBE) is known to increase peripheral blood circulation. The hypothesis that GBE may be able to enhance radiosensitivity of tumor by improving tumor blood flow and thus decreasing hypoxic fraction was tested. MATERIALS AND METHODS Fibrosarcoma (FSaII) growing in C3H mouse leg muscle was used as a tumor model. GBE was given i.p. 1 h before irradiation with or without priming dose given 1 day earlier. Effect on tumor and normal tissue radiation reaction was investigated. RESULTS Tumor growth delay by radiation was more elongated after two doses (1-day interval) of GBE than after a single dose. Radiation dose for 3-day tumor growth delay was decreased from 12.45 (10.97-13.93) Gy to 6.06 (3.89-8.22) Gy by two doses of GBE [enhancement ratio = 2.06 (1.32-2.79)]. Hypoxic cell fraction was 10.6% (6.3-18.2%) for control, 7.2% (3.8-14.0%) after a single dose (P = 0.18) and 2.7% (1.5-5.0%) after two doses (P < 0.001). Radiation effect on normal tissue, estimated by acute skin reaction and jejunal crypt assay, was not affected by GBE. CONCLUSION Ginkgo biloba extract enhances radiation effect on tumor without increasing acute normal tissue radiation damage in this model system probably by increasing tumor blood flow and further investigation for this possible radiosensitizer is needed.
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Affiliation(s)
- S W Ha
- Laboratory of Radiation Biology, Seoul National University Medical College, South Korea
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