Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F27: Superconductivity:Mostly_Kagome |
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Sponsoring Units: DCMP Chair: Gediminas Simutis, Paul Scherrer Institute Room: Room 219 |
Tuesday, March 7, 2023 8:00AM - 8:12AM Author not Attending |
F27.00001: Nodeless superconductivity in kagome metal CsV3Sb5 with and without time-reversal symmetry breaking Swee K Goh, 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 Evidence for time-reversal symmetry breaking (TRSB) inside the charge-density-wave (CDW) phase of the kagome superconductor CsV3Sb5 has been accumulating. Hence, the superconductivity in CsV3Sb5 emerges from a TRSB normal state, potentially resulting in an exotic superconducting state. To reveal the pairing symmetry, we first investigate the effect of nonmagnetic impurity. Our results show that the superconducting critical temperature is insensitive to disorder, pointing to conventional s-wave superconductivity. Moreover, our measurements of the self-field critical current (Ic,sf), which is related to the London penetration depth, also confirm conventional s-wave superconductivity with strong coupling. Finally, we measure Ic,sf where the CDW order is removed by pressure and superconductivity emerges from the pristine normal state. Our results show that s-wave gap symmetry is retained, providing strong evidence for the presence of conventional s-wave superconductivity in CsV3Sb5 irrespective of the presence of the TRSB. |
Tuesday, March 7, 2023 8:12AM - 8:24AM |
F27.00002: Study of magnetotransport properties in the novel kagome superconductor CsV3Sb5 Supeng Liu, Masaki Roppongi, Kota Ishihara, Brenden Ortiz, Stephen D Wilson, Romain Grasset, Marcin Konczykowski, Kenichiro Hashimoto, Takasada Shibauchi Kagome lattice systems provide a platform for a rich variety of novel quantum phases of matter, such as quantum spin liquids, Dirac/Wyle fermions, unconventional superconductivity, and charge/spin order, owing to their frustrated geometry and non-trivial topological nature. Recently, a new family of kagome superconductors AV3Sb5 (A = K, Rb, Cs) has attracted tremendous attention because of their unique band structure with van Hove singularities and Dirac dispersions. All the members show unconventional charge-density-wave (CDW) order with time-reversal symmetry breaking. Very interestingly, a non-monotonic Hall coefficient anomaly has been reported below TCDW. Various possibilities, such as Berry curvature, skew scattering, and loop current, have been proposed as the origin, but it has not yet been clarified. |
Tuesday, March 7, 2023 8:24AM - 8:36AM |
F27.00003: Quantum oscillations in the Kagome superconductors AV3Sb5 (A = K, Rb, Cs) Frederic Hardy, Liran Wang, Anmol Shukla, Amir A Haghighirad, Mingquan He, Wei Xia, Yanfeng Guo, Christoph Meingast The layered Kagome metals AV3Sb5 (A = K, Rb, Cs) exhibit a unique combination of nontrivial band topology, competing charge- and superconducting orders and clear signatures of electron correlations. Using thermodynamic (magnetization, magnetostriction, thermal expansion) and transport measurements, we have investigated the normal- and superconducting state properties of high-quality single crystals. Clear signatures of quantum oscillations were observed in all these quantities. The nature of the Fermi surface in the CDW state and the interplay with superconductivity is discussed in the light of recent theoretical models. |
Tuesday, March 7, 2023 8:36AM - 8:48AM |
F27.00004: The nature of the CDW in Kagome Superconductors AV3Sb5 from the perspective of electronic structure Xianxin Wu, Yong Hu, Brenden Ortiz, Nicholas C Plumb, Stephen D Wilson, Andreas P Schnyder, Ming Shi The recently discovered layered kagome metals AV3Sb5 (A=K, Rb, Cs) have attracted much attention because of their unique combination of superconductivity, charge density wave (CDW) order, and nontrivial band topology. The CDW order with an in-plane 2x2 reconstruction is found to exhibit exotic properties, such as time-reversal symmetry breaking and rotational symmetry breaking. However, the nature of the CDW, including its dimensionality, structural pattern, and effect on electronic structure, remains elusive despite intense research efforts. Here, we present a comprehensive study on the electronic structure of AV3Sb5 by combining angle-resolved photoemission spectroscopy with Density Functional theory calculations. Apart from the energy shift of van Hove singularities, we observe doubleband splittings for V d-orbital bands in the CDW phase, which provides essential information for revealing the dimensionality and pattern of the CDW order. Our calculations show that three-dimensional CDW orders containing stacking of Star-of-David and Tri-Hexagonal patterns along the c axis can quantitatively reproduce the experimental features. These results provide crucial insights into the nature and distortion pattern of the CDW order, and its signature in the electronic structure, thereby laying down the basis for a substantiated understanding of the exotic properties in the family of AV3Sb5 kagome metals. |
Tuesday, March 7, 2023 8:48AM - 9:00AM |
F27.00005: Strong-coupling effects in the kagome CDW system CsV3Sb5 Leander Peis, Ge He, Emma F Cuddy, Dong Li, Brian Moritz, Haitao Yang, Hongjun Gao, Thomas Devereaux, Rudolf U Hackl We present a polarization-dependent Raman scattering study of the kagome metal CsV3Sb5, focusing on the charge density wave (CDW). We resolve several signatures of strong-coupling between the lattice and the electronic system. First, the energy of the A1g Γ-point phonon exhibits a discontinuity at the phase transition temperature TCDW = 95 K. Second, the magnitude of the observed CDW-energy gap 2Δ is compatible with strong coupling. The gap ratio 2Δ/kBTCDW exceeds the weak coupling limit of 3.52 by a factor of 6 in both A1g and E2g symmetry. Third, the observed A1g amplitude mode depends weaker on temperature than expected and displays an asymmetric Fano-type line shape, particularly around 70K. We interpret this deviation in terms of strong coupling between the phonon-like amplitude mode and the electronic continuum. To the best of our knowledge such an asymmetry of an amplitude mode has not been observed before. |
Tuesday, March 7, 2023 9:00AM - 9:12AM |
F27.00006: Theoretical and Computational Analysis of Electron Phonon Coupling in CsV3Sb5 Emma F Cuddy, Ge He, Leander Peis, Dong Li, Ramona Stumberger, Brian Moritz, Haitao Yang, Hong-Jun Gao, Rudi Hackl, Thomas Devereaux CsV3Sb5 exhibits both charge density wave and superconducting phases. It is part of a class of kagome lattices that also have a notable band structure consisting of a Dirac dispersion and Weyl nodes. Because of apparent competition between the charge density wave (CDW) and superconductivity, it is critical to understand the interplay between electronic and phonon responses. In this talk we will present theoretical and computational investigation of the Raman spectra and electron-phonon coupling in this material, both in the CDW and in the undistorted arrangement, examining the electronic coupling to A1g and E2g phonons. A Fano lineshape for the A1g phonon indicates a strong coupling to the electron continuum. We observe that the line shape changes in the CDW state and a general agreement between first principle investigation and experiment is found. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F27.00007: Nature of unconventional pairing and competing Fermi surface instabilities in Kagome metals Matteo Dürrnagel, Tilman Schwemmer, Hendrik Hohmann, Domenico Di Sante, Xianxin Wu, Werner R Hanke, Ronny Thomale Multi-pocket Fermiologies are nearly inevitable for a large range of unconventional superconductors with multi-orbital and multi-sublattice structure. The Kagome three-sublattice structure of corner sharing triangles, even in a most simplistic single orbital abstraction, already gives rise to an intricate composition of Fermi level eigenstates. As a consequence, the distinct van Hove points of a Kagome band structure experience radically different sublattice occupation. Invoking that the dominant fluctuations are determined by the coupling between the van Hove points, a local Hubbard interaction term is unable to couple them due to mismatched sublattice weight, an effect we call sublattice interference. In this talk, we will show how the suppression of this usually most dominant interaction scale allows subleading effects like nearest-neighbour interactions to dictate the pairing tendencies of the system and analyse the resulting exotic states of matter. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F27.00008: Probing structural deformations of the Kagome metal CsV3Sb5 using X-ray diffraction temperature clustering (X-TEC) Krishnanand M Mallayya, Linus Kautzsch, Stephen D Wilson, Eun-Ah Kim
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Tuesday, March 7, 2023 9:36AM - 9:48AM |
F27.00009: Is Ba3In2O6 a high-Tc superconductor? Felix V Hensling, Michelle A Smeaton, Diana Dahliah, Bishal Shrestha, Nikolas Podraza, Geoffroy Hautier, Lena F Kourkoutis, Darrell G Schlom Immediately following its first synthesis in the 1980’s Ba3In2O6 was, due to its structural similarity to La(2-x)SrxCaCu2O6 and La2CaCu2O(6+δ), hypothesized to be a high-Tc superconductor.1 Ba3In2O6 being highly hygroscopic, however, inhibited any characterization of its transport properties. In the following years the material was all but forgotten until recently machine learning predicted its Tc to be 45.9 K.2 To answer the question whether Ba3In2O6 is a high Tc superconductor, Ba3In2O6 films were grown by molecular-beam epitaxy and capped by amorphous SiO2.3 The indium species were supplied by a newly developed suboxide source emanating a beam of In2O.3,4 In the course of successfully growing epitaxial Ba3In2O6 films, the previously unknown member of the same Ruddlesden-Popper series, Ba4In2O7, was also epitaxially grown.3 Despite the high quality of our films, which were probed by x-ray diffraction and scanning tunneling microscopy, Ba3In2O6 turns out to be insulating. Optical bandgap measurements of the epitaxial films by ellipsometry reveal a higher-than-expected bandgap (3.0 eV in-plane and 2.8 eV out-of-plane). We present different doping strategies and utilize first-principles calculations to show why all of them have been unsuccessful so far. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F27.00010: Using artificial intelligence techniques to aid the search for new superconducting materials Evan E Kim, Benjamin Roter, Nemanja Ninkovic For decades the search for new superconductors has relied on |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F27.00011: Superconductivity induced by pressure-induced anisotropic strain in Cux(CuI)0.002Bi2Te2.7Se0.3 crystal Min-Nan Ou, Fan-Yun Chiu, Yang-Yuan Chen, Chih-Ming Lin, Vankayala K Ranganayakulu The topological insulators Bi2Te3, Bi2Se3, and Sb2Te3 are found to present superconductivity (SC) at high pressure, however, the revealing of SC in Cu intercalated Bi2Se3 implies that they may share the same origin. Indeed, the presence of onset superconducting transition found at about 4 K at 6.6 GPa supports this speculation. To find the mechanism of causing SC, the copper intercalated crystal Cux(CuI)0.002Bi2Te2.7Se0.3 is fabricated to study the SC at high pressures. In this work, the temperature-dependent electrical resistance was measured by a homemade cryogenic electrical measurement system with temperatures down to 1.3 K and a magnetic field up to 9 Tesla at pressures of 0.8 through 36 GPa. The pressure-dependent XRD patterns are also gathered at pressures from 2 through 45 GPa. The first SC-like transition was detected at 3.8 GPa with Tc = 2 K. Upon further pressure increase; they reached maximum Tc = 9.3 K at 15 GPa. Interestingly, however, the XRD results suggest no obvious lattice phase transition until 13.9 GPa. Furthermore, the carrier concentration studied by Hall measurements is also indicating a dramatically up-turn in the magnitude of the power from ~ 1017 cm-3 to ~ 1022 cm-3 in the range of ~3 GPa through 15 GPa. The pressure-dependent carrier concentration, resistivity, and superconductivity Tc strongly imply an electronic phase transition embedded in the ambient pressure crystal phase. The strain analysis on (101) and (015) planes suggest that the hidden electronic phase transition may be induced by the anisotropic strain in the Cux(CuI)0.002Bi2Te2.7Se0.3. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F27.00012: Superconductivity from repulsive interactions on the kagome lattice Brian M Andersen, Roser Valenti, Astrid T Rømer, Morten Holm Christensen, Shinibali Bhattacharyya The discovery of superconductivity in layered vanadium-based kagome metals $A$V$_3$Sb$_5$ ($A$: K, Rb, Cs) has added a new family of materials to the growing class of possible unconventional superconductors. However, the nature of the superconducting pairing in these materials remains elusive. We present a microscopic theoretical study of the leading superconducting instabilities on the kagome lattice based on spin- and charge-fluctuation mediated Cooper pairing. The applied methodology includes effects of both on-site and nearest-neighbor repulsive Coulomb interactions. Near the upper van Hove filling -- relevant for the $A$V$_3$Sb$_5$ materials -- we find a rich phase diagram with several pairing symmetries being nearly degenerate. In particular, while a substantial fraction of the phase diagram is occupied by a spin-singlet order parameter transforming as a two-dimensional irreducible representation of the point group, several nodal spin-triplet pairing states remain competitive. We compute the band and interaction parameter-dependence of the hierarchy of the leading superconducting instabilities, and determine the detailed momentum dependence of the resulting preferred gap structures. Crucially, for moderate values of the interaction parameters, the individual pairing states depend strongly on momentum and exhibit multiple nodes on the Fermi surface. We discuss the properties of these superconducting gap structures in light of recent experimental developments of the $A$V$_3$Sb$_5$ materials. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F27.00013: Sublattice Interference promotes Pair Density Wave in Kagome Metals Yi-Ming Wu, Ronny Thomale, Srinivas Raghu We show that at the p-type van Hove filling in a Kagome lattice, the sublattice interference provides the microscopic basis for the formation of a pair density wave state at intermediate coupling strength. We first show that the sublattice interference allows for a simple identification of lattice interactions on band fermions. And from analyzing how the interactions are renormailized when the energy scale is lowered, we find that the Hubbard repulsion U becomes weaker, while other interactions such as nearest neighbor density repulsion V, on-bond exchange interaction J0 and bond pair hopping J1 can be significantly enhanced. Next, using mean field analysis, we find that both V and J1 can be attractive at finite momentum, and, if strong enough, can give rise to the pair density wave order. In cases when J0 becomes large, bond charge order may also arise. We argue that this establishes the microscopic foundation for pair density waves in Kagome metals. |
Tuesday, March 7, 2023 10:36AM - 10:48AM |
F27.00014: Non-uniform vestigial charge-4e phase in the Kagome superconductor CsV3Sb5 Yue YU Pair density wave state and its vestigial charge-4e and 6e superconducting phases have been reported in the Kagome superconductor CsV3Sb5. By treating the charge density waves that are ordered at high temperatures as static backgrounds, we notice that all pair density waves have the same wavevector in the folded 2D Brillouin zone. This wavevector is at a high symmetry point and preserves time-reversal symmetry. The PDW state is thus neither ‘FF’-like nor ‘LO’-like. With this non-degenerate pair density wave, we illustrate the resulting necessity for the vestigial charge-4e phase to be non-uniform. We will also highlight the importance of disorder in stabilizing vestigial phases in a commensurate system. |
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