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 N24: Charge density Wave in Kagome MetalInvited
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Sponsoring Units: DCMP Chair: Qimiao Si, Rice University Room: Room 237 |
Wednesday, March 8, 2023 11:30AM - 12:06PM |
N24.00001: Cascade of symmetry-broken electronic phases in kagome superconductors AV3Sb5 Invited Speaker: Ilija Zeljkovic The kagome lattice of transition metal atoms provides an exciting platform to study the interplay of electronic correlations and band topology. Recently discovered non-magnetic kagome metals AV3Sb5 (A=K, Rb, Cs) set off an avalanche of theoretical and experimental work as rare superconductors in the kagome structure. Experiments uncovered numerous exotic electronic phenomena in these materials, including novel density waves, topological surface states, time-reversal symmetry breaking and potentially unconventional superconductivity. In this talk, I will discuss our experiments on AV3Sb5 where we uncovered a cascade of symmetry-broken electronic states emerging as the material is cooled down. Using variable-temperature spectroscopic imaging scanning tunneling microscopy, we first detect a high-temperature tri-directional charge order with a 2a0 period that breaks the translation symmetry of the lattice. As the system is cooled down towards the superconducting transition, we observe an additional breaking of the six-fold rotation symmetry, which persists through the superconducting transition. This rotation symmetry breaking is reflected in the emergence of an additional 4a0 charge-stipe order and strongly anisotropic coherent quasiparticles related to the kagome Vanadium bands. Our experiments reveal a complex landscape of electronic states that can co-exist on a kagome lattice, and provide intriguing parallels to high-Tc superconductors and twisted bilayer graphene. |
Wednesday, March 8, 2023 12:06PM - 12:42PM |
N24.00002: Field-tuned chiral transport in charge-ordered Kagome metal CsV3Sb5 Invited Speaker: Philip J Moll When electric conductors differ from their mirror image, unusual chiral transport coefficients appear that are forbidden in achiral metals, such as a non-linear electric response known as electronic magneto-chiral anisotropy (eMChA). While chiral transport signatures are by symmetry allowed in many conductors without a center of inversion, it reaches appreciable levels only in rare cases when an exceptionally strong chiral coupling to the itinerant electrons is present. So far, observations of chiral transport have been limited to materials in which the atomic positions strongly break mirror symmetries. Here, we discuss chiral transport in the centro-symmetric layered Kagome metal CsV3Sb5, observed via second harmonic generation under in-plane magnetic field. The eMChA signal becomes significant only at temperatures below 35 K, deep within its charge-ordered state at 94 K. This temperature dependence reveals a direct correspondence between electronic chirality and unidirectional charge order, and field-tunability would be a natural consequence of spontaneous time-reversal-symmetry breaking. We show that the chirality is set by the out-of-plane field component and that a transition from left- to right-handed transport can be induced by changing the field sign. CsV3Sb5 is the first material in which strong chiral transport can be controlled and switched by small magnetic-field changes, in stark contrast to structurally chiral materials – a prerequisite for their application in electronics. |
Wednesday, March 8, 2023 12:42PM - 1:18PM |
N24.00003: A tunable charge density wave in the kagome metal ScV6Sn6 Invited Speaker: William R Meier The frustrated interactions between atoms arranged on a kagome lattice produce a wonderful playground for unusual electronic and magnetic physics. Although magnetic frustration initially brought attention to kagome materials, the impact of the features of the electronic structure itself has garnered recent attention. For example, the charge density wave (CDW) in hexagonal-FeGe and AV3Sb5 compounds are closely tied to van Hove singularities in their electronic structure. |
Wednesday, March 8, 2023 1:18PM - 1:54PM |
N24.00004: Topological kagome charge order Invited Speaker: Jiaxin Yin Kagome lattice naturally features Dirac fermions, flat bands, and van Hove singularities in its electronic structure. The Dirac fermions encode topology, flat bands favor magnetism, while van Hove singularities can lead to instabilities towards long-range orders, altogether allowing for the discovery of a series of topological kagome magnets and superconductors. Recent progress in studying these kagome materials has witnessed rich emergent phenomena resulting from the quantum interactions between geometry, topology, and correlation. I will briefly review the recent progress in this field and discuss our work on finding the topological kagome charge order with advanced spectroscopic techniques, and highlight the magnetic tunability and bulk-boundary correspondence of this novel quantum order. |
Wednesday, March 8, 2023 1:54PM - 2:30PM |
N24.00005: Intertwined magnetism and charge density wave order in kagome FeGe Invited Speaker: Ming Yi Electron correlations often lead to emergent orders in quantum materials. Kagome lattice materials are emerging as an exciting platform for realizing quantum topology in the presence of electron correlations. This proposal stems from the key signatures of electronic structures associated with its lattice geometry: flat band induced by destructive interference of the electronic wavefunctions, topological Dirac crossing, and a pair of van Hove singularities (vHSs). A plethora of correlated electronic phases have been discovered amongst kagome lattice materials, including magnetism, charge density wave (CDW), nematicity, and superconductivity. These materials can be largely organized into two types: those that host magnetism and those that host CDW order. Recently, a CDW order has been discovered in the magnetic kagome FeGe, providing a new platform for understanding the interplay between CDW and magnetism. Here, utilizing angle-resolved photoemission spectroscopy, we observe all three types of electronic signatures of the kagome lattice: flat bands, Dirac crossings, and vHSs. From both the observation of a temperature-dependent shift of the vHSs towards the Fermi level as well as guidance via first-principle calculations, we identify the presence of the vHSs near the Fermi level (EF) to be driven by the development of underlying magnetic exchange splitting. Furthermore, we show spectral evidence for the CDW order as gaps that open on the near-EF vHS bands, as well as evidence of electron-phonon coupling from a kink on the vHS band together with phonon hardening observed by inelastic neutron scattering. Our observation points to the magnetic interaction-driven band modification resulting in the formation of the CDW order, indicating an intertwined connection between the emergent magnetism and vHS charge order in this moderately-correlated kagome metal. |
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