Charge-density-wave-induced bands renormalization and energy gaps in a kagome superconductor RbV3Sb5

Abstract

Recently discovered Z 2 topological kagome metals AV 3 Sb 5 (A = K, Rb, and Cs) exhibit intriguing transport anomalies and novel superconducting paring states, providing a versatile platform for studying interplay between electron correlation and quantum orders. Here we directly visualise how temperature drives band renormalization and Lifshitz transition in RbV 3 Sb 5 using angle-resolved photoemission spectroscopy, pointing to the key role of tuning van Hove singularities to the Fermi energy in mechanisms of both CDW and superconducting orders. Multiple singularities with different energies and orbital characters could induce various ordering phases, including superconductivity if cooperating with matching bosons. Considering the existence of the nontrivial topological Dirac surface states at the time-reversal-invariant momentum points, they may also provide a promising route to realize zero energy modes related to Majorana fermions. Our findings are significant in understanding abundant transport behaviors and quantum phases in these kagome superconductors.

Multiple Energy Scales and Anisotropic Energy Gap in the Charge-Density-Wave Phase of Kagome Superconductor CsV3Sb5

“…Besides superconductivity, AV 3 Sb 5 commonly undergoes a charge-density wave (CDW) transition at T CDW = 78-103 K accompanied with threedimensional (3D) 2×2×2 charge order [27,28]. Angleresolved photoemission spectroscopy (ARPES) clarified that the kagome-lattice bands participate in the states near the Fermi level (E F ), by observing the Dirac-conelike bands forming a large hexagonal Fermi surface (FS) centered at the Γ point and a saddle point near E F at the M point, together with an electron pocket at the Γ point of 2D Brillouin zone (BZ), consistent with the densityfunctional-theory (DFT) calculations [25,27,29,30].…”

Electronic instabilities of kagome metals: saddle points and Landau theory

“…Angle resolved photoemission studies show these materials to be multi-band systems with several Fermi surface components [39], including approximately nested components and a Fermi energy that is close to multiple saddle points of the dispersion, in agreement with density functional theory [39,40]. Furthermore, strong momentum dependent charge gaps near the saddle point momenta were observed below the CDW transition temperature [41,42].…”

Electronic properties of correlated kagomé metals AV$_3$Sb$_5$(A = K, Rb, Cs): A perspective

“…While ARPES measurements have established the Z 2 topology, high-resolution ARPES has also served to visualize the temperature-driven band renormalization [19] and the momentum dependence of the CDW gap (largest near M, gapless or small gap near the Dirac cones) [20][21][22]; whereupon they indicate how the CDW is driven by the scattering of electrons between neighboring M saddle points in the Brillouin zone. The band renormalization supports the evidence of a three-dimensional charge order.…”