Rich nature of Van Hove singularities in Kagome superconductor CsV3Sb5

Abstract

The recently discovered layered kagome metals AV3Sb5 (A = K, Rb, Cs) exhibit diverse correlated phenomena, which are intertwined with a topological electronic structure with multiple van Hove singularities (VHSs) in the vicinity of the Fermi level. As the VHSs with their large density of states enhance correlation effects, it is of crucial importance to determine their nature and properties. Here, we combine polarization-dependent angle-resolved photoemission spectroscopy with density functional theory to directly reveal the sublattice properties of 3d-orbital VHSs in CsV3Sb5. Four VHSs are identified around the M point and three of them are close to the Fermi level, with two having sublattice-pure and one sublattice-mixed nature. Remarkably, the VHS just below the Fermi level displays an extremely flat dispersion along MK, establishing the experimental discovery of higher-order VHS. The characteristic intensity modulation of Dirac cones around K further demonstrates the sublattice interference embedded in the kagome Fermiology. The crucial insights into the electronic structure, revealed by our work, provide a solid starting point for the understanding of the intriguing correlation phenomena in the kagome metals AV3Sb5.

Charge density wave in kagome lattice intermetallic ScV6Sn6

“…The Fermi level sits within vanadium d-orbital bands in both the AV 3 Sb 5 compounds [22,25,27,28,40,57] and GdV 6 Sn 6 [43,44,46]. It is likely that the vanadium bands play a key role in CDW formation in ScV 6 Sn 6 as they do in the AV 3 Sb 5 compounds [25,[27][28][29].…”

“…Stacked vanadium kagome layers in this material give rise to a charge density wave (CDW) and superconductivity. The origin of the CDW is closely tied to van Hove singularities at Fermi level [26][27][28][29]. The unusual characteristic of the CDW [23,27,[30][31][32][33][34][35]] and it's interaction with superconductivity [36][37][38][39] have sparked great interest in kagome lattice derived charge order [40].…”

Universal three-state nematicity and magneto-optical Kerr effect in the charge density waves in AV$_3$Sb$_5$ (A=Cs, Rb, K)

“…The kagome lattice provides a fascinating playground to study geometrical frustration, topology and strong correlations [1][2][3][4][5][6][7][8][9][10][11][12][13]. The newly discovered kagome metals AV3Sb5 (A=K, Rb, Cs) exhibit various interesting phenomena including topological band structure [14][15][16][17][18], symmetry-breaking charge density waves (CDWs) [16,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] and superconductivity [14,15,[38][39][40][41]. Nevertheless, the nature of the symmetry breaking in the CDW phase is not yet clear, despite the fact that it is crucial to understand whether the superconductivity is unconventional.…”

Tunable Topological Dirac Surface States and Van Hove Singularities in Kagome Metal GdV6Sn6

“…In addition, various forms of magnetism in the lowtemperature electronic ground state enable the realization of quantum-limit Chern topological magnetism [8]. Besides these intensively studied magnetic kagome materials, the recently discovered non-magnetic kagome metals AV3Sb5 (A=K, Rb, Cs) were found to possess a unique combination of novel correlated phenomena and nontrivial band topology [9,10,[16][17][18][19][20]]. An intriguing chiral CDW instability [21,22] and superconductivity [10,16,17] have been observed in the absence of magnetic orders, suggesting that the vanadium kagome lattice is an ideal platform for investigating correlated quantum states.…”

“…1e, where four VHS points emerge at the M in the vicinity of EF (indicated by the red arrows and labeled as VHS1-4). A closer examination of the orbitally decomposed electronic structure from DFT indicates that the states of VHS1, VHS2 and VHS3 at the M point, characterized by V dxz, dxy and dz2 orbitals, are solely attributed to one sublattice in the V kagome lattice, and thus are of p-type [19,20,27]. In contrast, the states of VHS4 at the M point are attributed to a mixture of two sublattices, and thus are of of m-type (for details, see Supplementary S1).…”