Emergence of New van Hove Singularities in the Charge Density Wave State of a Topological Kagome Metal RbV3Sb5

Abstract

Quantum materials with layered kagome structures have drawn considerable attention due to their unique lattice geometry, which gives rise to flat bands co-existing with Dirac-like dispersions. The interplay between strong Coulomb correlations and nontrivial band topology in these systems results in various exotic phenomena. Recently, vanadium-based materials with layered kagome structures are discovered to be topological metals, which exhibit charge density wave (CDW) properties, significant anomalous Hall effect, and unusual superconductivity at low temperatures. Here we exploit high-resolution angle-resolved photoemission spectroscopy to investigate the electronic structure evolution induced by the CDW transition in a vanadium-based kagome material RbV3Sb5. A remarkable band renormalization in the CDW state is observed, which is consistent with first principles calculations based on an inverse star-of-David superstructure. The CDW phase transition gives rise to a partial energy gap opening at the Fermi level, a shift in the band dispersion, and most importantly, the emergence of new van Hove singularities associated with large density of states, which are absent in the normal phase and may be related to superconductivity observed at lower temperatures. Our work would shed light on the microscopic mechanisms for the formation of the CDW and superconducting states in these topological kagome metals.

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.…”

Optical study of RbV$_3$Sb$_5$: Multiple density-wave gaps and phonon anomalies

“…Additionally, we are able to pinpoint two distinct CDW gaps in RbV 3 Sb 5 . These gaps are integral to the putative topological state but could be previously observed with surface-sensitive techniques only [12,29]. Our optical study confirms their bulk nature, thus setting a benchmark for the CDW state of AV 3 Sb 5 .…”

“…As noted by the arrow, the elastic scattering shows a slight change across the CDW transition. Considering the partial gapping of the Fermi surface [12,29] and the slight change of the carrier density across T CDW , this small change is expected. On the other hand, the backscattering mechanism seems to be unaffected by the CDW.…”

Fermiology and Origin of Tc Enhancement in a Kagome Superconductor Cs(V1-xNbx)3Sb5

“…Recently, a family of kagome metals AV 3 Sb 5 (AVS; A = K, Rb, Cs) with a V kagome network [Fig. 1(a)] has emerged [23] as a new platform to study the physics associated with the SP due to its proximity to E F , as revealed by density-functional-theory calculations [23][24][25][26][27][28][29][30][31][32] and angle-resolved photoemission spectroscopy (ARPES) [33][34][35][36][37][38][39]. AVS commonly exhibits superconductivity (T c = 0.9-2.5 K) and charge-density wave (CDW; T CDW = 78-103 K) [27,40,41].…”