Article
Chemistry, Multidisciplinary
Wei Zhang, Xinyou Liu, Lingfei Wang, Chun Wai Tsang, Zheyu Wang, Siu Tung Lam, Wenyan Wang, Jianyu Xie, Xuefeng Zhou, Yusheng Zhao, Shanmin Wang, Jeff Tallon, Kwing To Lai, Swee K. Goh
Summary: The kagome metal CsV3Sb5 exhibits an unusual competition between charge-density-wave (CDW) order and superconductivity. Time reversal symmetry breaking (TRSB) has been observed inside the CDW phase, indicating the emergence of superconductivity from a TRSB normal state and potentially leading to an exotic superconducting state. Through various experiments, it has been confirmed that CsV3Sb5 shows conventional s-wave superconductivity, which is insensitive to disorder and exhibits strong coupling, even in the presence or absence of TRSB.
Article
Multidisciplinary Sciences
Huimin Zhang, Basu Dev Oli, Qiang Zou, Xu Guo, Zhengfei Wang, Lian Li
Summary: In FeSn, we observe the symemtry-breaking and tunable electronic orders in the Kagome lattice by applying a magnetic field, providing a new avenue for studying the unique quantum states in Kagome lattice.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Sudeep Kumar Ghosh, James F. Annett, Jorge Quintanilla
Summary: The study proposes a novel superconducting ground state where microscopic supercurrent loops spontaneously form within a unit cell at the superconducting transition temperature, breaking time-reversal symmetry in the superconducting state. Using Ginzburg-Landau theory, the emergence of these currents in a toy model is detailed, along with the crystallographic symmetry requirements to realize such a state. An upper bound for the resulting internal magnetic fields is estimated and found to be consistent with recent muon-spin relaxation experiments.
NEW JOURNAL OF PHYSICS
(2021)
Review
Multidisciplinary Sciences
Kun Jiang, Tao Wu, Jia-Xin Yin, Zhenyu Wang, M. Zahid Hasan, Stephen D. Wilson, Xianhui Chen, Jiangping Hu
Summary: This review discusses the recent progress on the experimental and theoretical studies of kagome superconductors AV(3)Sb(5), including the electronic properties, charge density wave state, time-reversal symmetry breaking, and superconducting properties. The authors aim to stimulate an expanded search for unconventional kagome superconductors.
NATIONAL SCIENCE REVIEW
(2023)
Article
Materials Science, Multidisciplinary
Alexei M. Tsvelik, Saheli Sarkar
Summary: The recently discovered kagome metals AV(3)Sb(5) offer a promising avenue to study exotic phases resulting from the interplay between electronic correlations and topology. These materials exhibit superconductivity and a charge-density-wave (CDW) phase at around 100K, yet the origin of the CDW phase remains unknown. The presence of a robust multicomponent CDW phase with an unusually large anomalous Hall effect makes these systems particularly interesting. In weakly coupled quasi-two-dimensional systems, fluctuation-driven exotic phases may arise. Our findings suggest the possible existence of a fluctuation-driven regime of composite CDW order in thin films of kagome metals above the CDW transition temperature.
Article
Multidisciplinary Sciences
Yuki M. Itahashi, Toshiya Ideue, Shintaro Hoshino, Chihiro Goto, Hiromasa Namiki, Takao Sasagawa, Yoshihiro Iwasa
Summary: The authors observe second-order nonlinear transport in time-reversal-symmetric PbTaSe2, where the nonlinearity is enhanced in the superconducting state.
NATURE COMMUNICATIONS
(2022)
Article
Materials Science, Multidisciplinary
Yongkai Li, Qing Li, Xinwei Fan, Jinjin Liu, Qi Feng, Min Liu, Chunlei Wang, Jia-Xin Yin, Junxi Duan, Xiang Li, Zhiwei Wang, Hai-Hu Wen, Yugui Yao
Summary: The coexistence of superconductivity and charge-density wave (CDW) order in kagome systems has sparked great interest. In this study, Cs(V1-xNbx)3Sb5 samples with systematic Nb doping were extensively investigated, and it was found that Nb doping leads to the suppression of CDW order and the promotion of superconductivity. Additionally, the anomalous Hall effect (AHE) and magnetoresistance (MR) were significantly weakened along with the CDW order. The effects were interpreted through density-functional calculations and antiphase shifts of the Fermi energy near saddle points and a Fermi surface reorganization. The results uncovered a delicate and unusual competition between CDW order and superconductivity.
Article
Multidisciplinary Sciences
Xilin Feng, Kun Jiang, Ziqiang Wang, Jiangping Hu
Summary: The study identifies a chiral flux phase in the quasi-2D Kagome superconductor AV(3)Sb(5), which has the lowest energy and exhibits 2 x 2 charge orders observed experimentally. This phase breaks time-reversal symmetry and displays anomalous Hall effect.
Article
Materials Science, Multidisciplinary
Hong-Min Jiang, Ming-Xun Liu, Shun-Li Yu
Summary: Motivated by recent experimental evidence of chiral charge order in vanadium-based kagome superconductors, this theoretical investigation explores the impact of chiral flux charge order on normal and superconducting properties. The study finds that chiral flux charge order partially gaps the spectral weight on the Fermi surface, but preserves spectral weight on certain points, resulting in consistent energy gap patterns. Additionally, the investigation reveals that chiral flux charge order transforms a conventional fully gapped superconducting state into a nodal gap feature, accompanied by changes in density of states. These findings can potentially explain divergent experimental outcomes regarding superconducting pairing symmetry.
Article
Engineering, Electrical & Electronic
Sheng-Chin Ho, Ching-Hao Chang, Yu-Chiang Hsieh, Shun-Tsung Lo, Botsz Huang, Thi-Hai-Yen Vu, Carmine Ortix, Tse-Ming Chen
Summary: Research has shown that lithographically patterned strain can create a non-trivial band structure and exotic phase of matter in bilayer graphene.
NATURE ELECTRONICS
(2021)
Article
Physics, Multidisciplinary
Bo Liu, Min-Quan Kuang, Yang Luo, Yongkai Li, Cheng Hu, Jiarui Liu, Qian Xiao, Xiquan Zheng, Linwei Huai, Shuting Peng, Zhiyuan Wei, Jianchang Shen, Bingqian Wang, Yu Miao, Xiupeng Sun, Zhipeng Ou, Shengtao Cui, Zhe Sun, Makoto Hashimoto, Donghui Lu, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Luca Moreschini, Alessandra Lanzara, Yao Wang, Yingying Peng, Yugui Yao, Zhiwei Wang, Junfeng He
Summary: In the bismuth-based kagome metal CsTi3Bi5, the electronic instability can be investigated by tuning the van Hove singularity (vHS), which is different from other kagome metals like CsV3Sb5.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Glenn Wagner, Chunyu Guo, Philip J. W. Moll, Titus Neupert, Mark H. Fischer
Summary: This study provides a comprehensive symmetry classification of the possible charge orders in kagome materials and investigates the impact of external perturbations on these orders, offering a roadmap for future experimental tests.
Article
Materials Science, Multidisciplinary
Glenn Wagner, Chunyu Guo, Philip J. W. Moll, Titus Neupert, Mark H. Fischer
Summary: This article investigates possible charge ordering in kagome materials and provides further understanding through symmetry classification and studying the effects of external perturbations.
Article
Physics, Multidisciplinary
Titus Neupert, M. Michael Denner, Jia-Xin Yin, Ronny Thomale, M. Zahid Hasan
Summary: Superconductivity and ordered states have been observed in a family of kagome materials, with lattice geometry, topological electron behavior, and competition between ground states playing key roles in determining material properties. The compounds KV3Sb5, CsV3Sb5, and RbV3Sb5 exhibit a kagome net of vanadium atoms, showing superconductivity at low temperatures and unusual charge order at high temperatures, connecting to the underlying topological nature of the band structure. This highlights the importance of these discoveries in the context of wider research efforts in topological physics and superconductivity, while also discussing open problems in this field.
Article
Physics, Multidisciplinary
C. Pepin, H. Freire
Summary: In this paper, the authors present their studies on the phase diagram of cuprate superconductors and propose field-theoretical concepts to explain the properties of these compounds. They introduce the concept of an emergent SU(2) symmetry that rotates between the superconducting and charge order parameters. They also discuss the presence of an emergent U(1) gauge field in the theory and its implications for the pseudogap transition and spectroscopic probes.
Review
Multidisciplinary Sciences
Kun Jiang, Tao Wu, Jia-Xin Yin, Zhenyu Wang, M. Zahid Hasan, Stephen D. Wilson, Xianhui Chen, Jiangping Hu
Summary: This review discusses the recent progress on the experimental and theoretical studies of kagome superconductors AV(3)Sb(5), including the electronic properties, charge density wave state, time-reversal symmetry breaking, and superconducting properties. The authors aim to stimulate an expanded search for unconventional kagome superconductors.
NATIONAL SCIENCE REVIEW
(2023)
Article
Chemistry, Multidisciplinary
Zi-Jia Cheng, Ilya Belopolski, Hung-Ju Tien, Tyler A. Cochran, Xian P. Yang, Wenlong Ma, Jia-Xin Yin, Dong Chen, Junyi Zhang, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Guangming Cheng, Md. Shafayat Hossain, Qi Zhang, Maksim Litskevich, Yu-Xiao Jiang, Nan Yao, Niels B. M. Schroeter, Vladimir N. Strocov, Biao Lian, Claudia Felser, Guoqing Chang, Shuang Jia, Tay-Rong Chang, M. Zahid Hasan
Summary: Kagome magnets offer a fascinating platform for studying topological quantum phenomena, with highly tunable properties resulting from the interplay between crystal structure, magnetization, and spin-orbit coupling. In this study, Weyl lines with strong out-of-plane dispersion are directly visualized in the A-A stacked kagome magnet GdMn6Sn6 using angle-resolved photoemission spectroscopy. Remarkably, the Weyl lines exhibit a strong magnetization-direction-tunable spin-orbit coupling gap and binding energy tunability when substituting Gd with Tb and Li, respectively. These findings demonstrate the potential of using magnetization direction and valence counting as efficient tuning knobs for controlling distinct 3D topological phases, and highlight the versatility of the AMn(6)Sn(6) material family for exploring emergent topological quantum responses.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Sen Shao, Jia-Xin Yin, Ilya Belopolski, Jing-Yang You, Tao Hou, Hongyu Chen, Yuxiao Jiang, Md Shafayat Hossain, Mohammad Yahyavi, Chia-Hsiu Hsu, Yuan Ping Feng, Arun Bansil, M. Zahid Hasan, Guoqing Chang
Summary: Recent experiments report the existence of a charge density wave (CDW) in the antiferromagnet FeGe, but the nature of the charge ordering and associated structural distortion is still unclear. By examining the structural and electronic properties of FeGe, our study reveals that the 2 x 2 x 1 CDW is likely due to Fermi surface nesting of hexagonal-prism-shaped kagome states. We find that the distortion in FeGe mainly occurs in the positions of Ge atoms in the kagome layers rather than Fe atoms. Through calculations and modeling, we demonstrate that this unconventional distortion is driven by the intertwining of magnetic exchange coupling and CDW interactions in this kagome material. The movement of Ge atoms also enhances the magnetic moment of the Fe kagome layers.
Article
Chemistry, Physical
Charlotte Pughe, Otto H. J. Mustonen, Alexandra S. Gibbs, Stephen Lee, Rhea Stewart, Ben Gade, Chennan Wang, Hubertus Luetkens, Anna Foster, Fiona C. Coomer, Hidenori Takagi, Edmund J. Cussen
Summary: Ba2CuTeO6 is a material with a two-leg spin ladder structure of Cu2+ cations, which can be chemically tuned by substituting non-magnetic Zn2+ at the Cu2+ site. The substitution partitions the spin ladders into clusters, leading to a transition from long-range order to spin-freezing as the Zn2+ substitution increases. This provides a well-controlled tuning of the magnetic disorder and a model system for studying defects and segmentation in low-dimensional quantum magnets.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Inorganic & Nuclear
Benjamin Kintzel, Michael Boehme, Daniel Plaul, Helmar Goerls, Nicolas Yeche, Felix Seewald, Hans -Henning Klauss, Andrei A. Zvyagin, Erik Kampert, Thomas Herrmannsdoerfer, Gwendolyne Pascua, Christopher Baines, Hubertus Luetkens, Winfried Plass
Summary: The trinuclear high-spin iron(III) complex [Fe3Cl3(saltag(Br))(py)(6)]ClO4 was synthesized and characterized. Magnetic measurements showed antiferromagnetic exchange between the iron(III) ions, resulting in a geometrically spin-frustrated ground state. High-field magnetization and muon-spin relaxation experiments confirmed the isotropic nature of the magnetic exchange and the absence of significant intermolecular interactions. The complex is considered an ideal candidate for studying spin-electric effects.
INORGANIC CHEMISTRY
(2023)
Article
Multidisciplinary Sciences
Yigui Zhong, Jinjin Liu, Xianxin Wu, Zurab Guguchia, J. -x. Yin, Akifumi Mine, Yongkai Li, Sahand Najafzadeh, Debarchan Das, Charles Mielke, Rustem Khasanov, Hubertus Luetkens, Takeshi Suzuki, Kecheng Liu, Xinloong Han, Takeshi Kondo, Jiangping Hu, Shik Shin, Zhiwei Wang, Xun Shi, Yugui Yao, Kozo Okazaki
Summary: The newly discovered kagome superconductors offer a promising platform to explore the interplay between band topology, electronic order, and lattice geometry. However, the nature of the superconducting ground state and the electron pairing symmetry in this system is still not well understood. In this study, we directly observed a nodeless and nearly isotropic superconducting gap in the momentum space of two different kagome superconductors using high-resolution and low-temperature angle-resolved photoemission spectroscopy. The unique properties of the superconducting gap are independent of charge order in the normal state. This comprehensive characterization provides essential information about the electron pairing symmetry in kagome superconductors and advances our understanding of superconductivity and intertwined electronic orders in quantum materials.
Article
Physics, Multidisciplinary
Xiaokun Teng, Ji Seop Oh, Hengxin Tan, Lebing Chen, Jianwei Huang, Bin Gao, Jia-Xin Yin, Jiun-Haw Chu, Makoto Hashimoto, Donghui Lu, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Garrett E. Granroth, Binghai Yan, Robert J. Birgeneau, Pengcheng Dai, Ming Yi
Summary: Electron correlations in quantum materials can lead to emergent orders, such as the topological states found in kagome lattice materials. These emergent orders are a result of the specific electronic band structure associated with the kagome lattice geometry. Various correlated electronic phases, including magnetism and superconductivity, have been discovered in kagome lattice materials. In this study, the authors observe all three electronic signatures of the kagome lattice in FeGe using angle-resolved photoemission spectroscopy and provide evidence for the interplay between magnetism and charge order in this material.
Article
Instruments & Instrumentation
Lars Gerchow, Sayani Biswas, Gianluca Janka, Carlos Vigo, Andreas Knecht, Stergiani Marina Vogiatzi, Narongrit Ritjoho, Thomas Prokscha, Hubertus Luetkens, Alex Amato
Summary: The pioneering work on Muon-induced x-ray emission (MIXE) technique was conducted at the Paul Scherrer Institute (PSI) in the 1980s for non-destructive assessment of elemental compositions. In recent years, this method has been improved and adopted at many muon facilities worldwide. The GermanIum Array for Non-destructive Testing (GIANT) setup at PSI is a dedicated MIXE spectrometer that offers excellent performance and has been used for various applications such as archaeological research and collaboration with the industry.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2023)
Article
Chemistry, Multidisciplinary
Ziga Gosar, Tina Arh, Kevin Jaksetic, Andrej Zorko, Wenhao Liu, Hanlin Wu, Chennan Wang, Hubertus Luetkens, Bing Lv, Denis Arcon
Summary: Quasi-one-dimensional electron systems exhibit instability towards long-range ordered phases at low temperatures. In this study, muon spin rotation and relaxation (& mu;SR) were used to investigate the superconducting state in Rb2Mo3As3, which has one of the highest critical temperatures Tc = 10.4 K among quasi-one-dimensional superconductors. The results show stronger damping below Tc due to the formation of a vortex lattice. Comparison of different models suggests that the s-wave scenario provides the best fit, but with an anomalously small superconducting gap ⠁0/Tc ratio of 2 ⠁0/kBTc = 2.74(1). However, the nodal p-wave or d-wave scenarios cannot be ruled out based on slightly worse fits, yielding more realistic ratios of 2 ⠁0/kBTc = 3.50(2) and 2 ⠁0/kBTc = 4.08(1), respectively.
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
(2023)
Article
Materials Science, Multidisciplinary
Omer M. Aksoy, Anirudh Chandrasekaran, Apoorv Tiwari, Titus Neupert, Claudio Chamon, Christopher Mudry
Summary: Fermi surfaces can undergo sharp transitions with topological character when higher-order singularities develop at the transition. Odd singularities appear in pairs within the Brillouin zone when time-reversal and inversion symmetries are present. The combination of enhanced density of states and nesting between the singularities leads to interaction-driven instabilities.
Article
Materials Science, Multidisciplinary
V. K. Anand, D. T. Adroja, C. Ritter, Debarchan Das, Harikrishnan S. Nair, A. Bhattacharyya, Leandro Liborio, Simone Sturniolo, F. L. Pratt, Duc Le, G. Andre, Hubertus Luetkens, A. D. Hillier, Z. Hossain
Summary: We present results of muon spin relaxation (mu SR), neutron powder diffraction (NPD), and inelastic neutron scattering (INS) investigations on polycrystalline Pr2Pd3Ge5. The polycrystalline compound exhibits two antiferromagnetic transitions, which were confirmed by heat capacity measurements. Magnetic Bragg peaks were observed in the magnetically ordered state, and the magnetic structure was determined to be a canted antiferromagnetic structure of ordered Pr3+ moments. In the paramagnetic state, crystal electric field (CEF) excitations were observed through INS, and a CEF level scheme was derived through analysis.
Article
Materials Science, Multidisciplinary
Vadim Grinenko, Rajib Sarkar, Shreenanda Ghosh, Debarchan Das, Zurab Guguchia, Hubertus Luetkens, Ilya Shipulin, Aline Ramires, Naoki Kikugawa, Yoshiteru Maeno, Kousuke Ishida, Clifford W. Hicks, Hans-Henning Klauss
Summary: Muon spin rotation/relaxation (μSR) and polar Kerr effect measurements provide evidence for a time-reversal symmetry breaking (TRSB) superconducting state in Sr2RuO4. However, the absence of a cusp in the superconducting transition temperature (Tc) vs stress and the absence of a resolvable specific heat anomaly at TRSB transition temperature (TTRSB) under uniaxial stress challenge a hypothesis of TRSB superconductivity. Recent μSR studies under pressure and with disorder indicate that the splitting between Tc and TTRSB occurs only when the structural tetragonal symmetry is broken. To further test such behavior, we measured Tc through susceptibility measurements and TTRSB through μSR, under uniaxial stress applied along a (110) lattice direction. We have obtained preliminary evidence for suppression of TTRSB below Tc, at a rate much higher than the suppression rate of Tc.
