Observation of Electronic Nematicity Driven by the Three-Dimensional Charge Density Wave in Kagome Lattice KV₃Sb₅

Abstract

Kagome superconductors AV3Sb5 (A = K, Rb, Cs) provide a fertile playground for studying intriguing phenomena, including nontrivial band topology, superconductivity, giant anomalous Hall effect, and charge density wave (CDW). Recently, a C 2 symmetric nematic phase prior to the superconducting state in AV3Sb5 drew enormous attention due to its potential inheritance of the symmetry of the unusual superconductivity. However, direct evidence of the rotation symmetry breaking of the electronic structure in the CDW state from the reciprocal space is still rare, and the underlying mechanism remains ambiguous. The observation shows unconventional unidirectionality, indicative of rotation symmetry breaking from six-fold to two-fold. The interlayer coupling between adjacent planes with π-phase offset in the 2 × 2 × 2 CDW phase leads to the preferred two-fold symmetric electronic structure. These rarely observed unidirectional back-folded bands in KV3Sb5 may provide important insights into its peculiar charge order and superconductivity.

Charge density waves in two-dimensional transition metal dichalcogenides

“…It can provide information not only on the size of the CDW gap, but also on the exact momentum and energy position of the gap in the reciprocal space with the temperature evolution of the gap size [25,39,40,[55][56][57]. ARPES also directly measures the electron band structure, and its folding due to the PLD and the formation of the superstructure, enabling a direct comparison to the advanced theoretical calculations [37,39,40,58]. Since photoemission is a hybrid of spectroscopy and scattering experiments, the details of lineshape, spectral weight distribution, and spectral weight transfer, all carry important information related to the underlying mechanism of quantum phases [57,[59][60][61].…”

Chemical effect on the Van Hove singularity in superconducting kagome metal AV3Sb5 (A = K, Rb, and Cs)

“…25–29 Discrepancies were also noted between recent nuclear quadrupole resonance (NQR) 30,31 and angle-resolved photoemission spectroscopy (ARPES) experiments. 32–35 The superconducting phase diagram as a function of doping appears to be different as well: A ‘second dome’ above 35% Sn doping was reported for A = Cs, 33,36 whereas KV 3 Sb 5 and RbV 3 Sb 5 seem to exhibit a single-dome superconductivity. 33,36,37 A qualitative difference in superconducting gap symmetry was also noticed.…”

Temperature-Driven Rotation Symmetry-Breaking States in an Atomic Kagome Metal KV3Sb5

“…Very recently, a new family of vanadium-based kagome metals AV 3 Sb 5 (A = K, Rb, Cs) with a nonmagnetic ground state was discovered. − Shortly afterward, rich electronic properties including the unconventional anomalous Hall effect, Z 2 topological invariant, , superconductivity, − roton pair density wave (PDW), and charge density wave (CDW) − have been realized in these systems. Particularly, the CDW behaviors among the AV 3 Sb 5 family are diverse.…”

“…KV 3 Sb 5 is a layered kagome superconductor composed of alternately stacked K layers and VSb slabs with hexagonal symmetry. In each VSb slab, the V kagome lattice is interweaved by three Sb hexagonal lattices, forming a sandwiched Sb 2 /VSb 1 /Sb 2 configuration, − as depicted in Figure a,b. Due to the stronger chemical bonding between V and Sb atoms, KV 3 Sb 5 is expected to cleave between the K layers and VSb slabs, thus exposing the K or Sb 2 surfaces.…”