AV3Sb5 band structure

\(AV_3Sb_5\) Band structure¶

• DFT calculations and ARPES measurements show multiple bands cross the Fermi level.
• The in-plane Sb \(p_z\) orbital forms one electron pocket around the \(\Gamma\) point, and the V d orbitals form multiple Fermi surface around the M points.
• It is very difficult to capture such a complicated Fermi surface topography in a simplified Tight-binding model.
• The essential electronic structure of \(AV_3Sb_5\) is widely believed to be dominated by the quasiparticles around the Van-Hove singularity points.
  1. Van-Hove singularity points lies very close to Fermi level as obtained from DFT and ARPES calculations.
  2. Dominant scattering momenta are 3Q (\(Qa, Qb,Q_c\)) related to three M points as well as the \(\Gamma\) point Fermi surface induced q1 scattering.
  3. Finally, the CDW gap size is maximum around the Van-Hove singularity points, while it vanishes at the \(\Gamma\) pocket.
  4. A minimal model capturing the Van-Hove singularity points and \(\Gamma\) point Fermi surface could faithfully describe the physics behind \(AV_3Sb_5\).
  5. A minimal 4 band model based on the V local \(d_{X^2−Y^2}\) orbital and in-plane Sb \(p_z\) orbital is proposed(arXiv).

Ref. Twofold van Hove singularity and origin of charge order in topological kagome superconductor CsV3Sb5 | Nature Physics

Prototypical tight-binding electronic structure of the kagome lattice. Dashed and solid lines are for the case with and without spin–orbit coupling, respectively. Two vHS at filling fractions n = 5/12 and n = 3/12 with diverging density of states are marked with grey shades in d. e, f, Fermi surface (FS) of the kagome lattice at the n = 5/12 filling with p-type vHS (e) and at the n = 3/12 filling with m-type vHS (f). Red, blue and green colours along the Fermi surface contour represent the distribution of three kagome sublattice weights. The nesting vector Q = (π, 0) and its symmetry equivalents are marked with black arrows. BZ, Brillouin zone.

Theoretical electronic structure of CsV3Sb5 from DFT. The solid arrows at K and H mark the multiple Dirac points (DP) emerging from the 3d orbital degrees of freedom in the V kagome net, while the dashed arrows mark the Dirac nodes emerging from the crossing between different kagome sets. Solid coral, blue and red lines indicate three saddle-like dispersions or vHS near the Fermi level and their \(k_z\) dependence along the M–L line.

Orbital-projected electronic structure of \(CsV_3Sb_5\)¶

• In CsV3Sb5, four dispersive bands cross the Fermi level. The orbital projection from DFT reveals that the G band has dominant Sb character.
• The vanadium kagome net mainly contributes to the Fermi contours near the zone boundary \(\bar{M}\) and \(\bar{K}\)

V \(d_{xy}/d_{x^2-y^2}\)	V \(d_{xz}/d_{yz}\)	V \(d_{z^2}\)