Electronic nature of charge density wave and electron-phonon coupling in kagome superconductor KV3Sb5

Abstract

The Kagome superconductors AV3Sb5 (A = K, Rb, Cs) have received enormous attention due to their nontrivial topological electronic structure, anomalous physical properties and superconductivity. Unconventional charge density wave (CDW) has been detected in AV3Sb5. High-precision electronic structure determination is essential to understand its origin. Here we unveil electronic nature of the CDW phase in our high-resolution angle-resolved photoemission measurements on KV3Sb5. We have observed CDW-induced Fermi surface reconstruction and the associated band folding. The CDW-induced band splitting and the associated gap opening have been revealed at the boundary of the pristine and reconstructed Brillouin zones. The Fermi surface- and momentum-dependent CDW gap is measured and the strongly anisotropic CDW gap is observed for all the V-derived Fermi surface. In particular, we have observed signatures of the electron-phonon coupling in KV3Sb5. These results provide key insights in understanding the nature of the CDW state and its interplay with superconductivity in AV3Sb5 superconductors.

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

“…The domains we observe are on the order of 100 µm scale, which explains the nematicity observed in transport experiments on macroscopic samples possibly due to unequal population of three domains [54,55]. Our results add strong constrains on interpreting other macroscopic measurements including photo-emission, x-ray and optical spectroscopy [17,26,30,35,36,57,60,61,[63][64][65][66][67].…”

“…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.…”

Microscopic structure of three-dimensional charge order in kagome superconductor AV3Sb5 and its tunability

“…2a, the DFT band calculation for CsV3Sb5 reveals four bands near EF: an electron-pocket at the Brillouin zone center G (G-band), dxy/dx2-y2 orbital kagome bands with Dirac point at » -0.27 eV and vHS near EF (K1-band), dxz/dyz orbital kagome bands with Dirac point at » -1.08 eV and vHS near EF (K2-band), and additional dxz/dyz orbital kagome bands with opposite parity from the K2-band (K2'-band). All band dispersions have been closely reproduced in previous ARPES studies 19,20,[36][37][38] . Meanwhile, we note that in the experimental geometry used in the present study, only G-, K1-, and K2-bands are visible in the ARPES spectra (see Fig.…”

Intertwining orbital current order and superconductivity in Kagome metal

“…1a. Based on the ab initio computation [12,18,21,24,30,31], it is known that the vHS near the Fermi level is mainly described by a single d orbital, d xy . Starting from the nearest-neighbour tight-binding model, there are three inequivalent vHS points in the Brillouin zone (BZ).…”