Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in $A$V$_{3}$Sb$_ {5}$ ($A = \text{K, Rb, Cs}$)

The recently discovered vanadium-based Kagome metals $A$ V $_{3}$ Sb $_{5}$ ( $A = K, Rb, Cs$ ) are of great interest with the interplay of charge density wave (CDW) order, band topology and superconductivity. In this paper, by identifying elementary band representations (EBRs), we construct a two-EBR graphene-Kagome model to capture the two low-energy van-Hove-singularity dispersions and, more importantly, the nontrivial band topology in these Kagome metals. This model consists of $A_{g} @ 3 g$ (V- $d_{x^{2} - y^{2} / z^{2}}$ , Kagome sites) and $A_{2}^{''} @ 2 d$ EBRs (Sb1- $p_{z}$ , honeycomb sites). We have investigated the Fermi surface instability by calculating the electronic susceptibility $χ (q)$ . Prominent Fermi-surface nesting peaks are obtained at three L points, where the $z$ component of the nesting vector shows intimate relationship with the anticrossing point along M–L. The nesting peaks at L are consistent with the $2 \times 2 \times 2$ CDW reconstruction in these compounds. In addition, the sublattice-resolved bare susceptibility is calculated and similar sharp peaks are observed at the L points, indicating a strong antiferromagnetic fluctuation. Assuming a bulk $s$ -wave superconducting pairing, helical surface states and nontrivial superconducting gap are obtained on the (001) surface. In analogous to FeTe $_{1 - x}$ Se $_{x}$ superconductor, our results establish another material realization of a stoichiometric superconductor with nontrivial band topology, providing a promising platform for studying exotic Majorana physics in condensed matter

Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in $A$ V $_{3}$ Sb $_{5}$ ( $A = K, Rb, Cs$ )

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Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in $A$ V $_{3}$ Sb $_{5}$ ( $A = K, Rb, Cs$ )

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Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in AAV33​Sb55​ (A=K, Rb, CsA=K, Rb, Cs)

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Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in AAV33​Sb55​ (A=K, Rb, CsA=K, Rb, Cs)

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Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in $A$ V $_{3}$ Sb $_{5}$ ( $A = K, Rb, Cs$ )

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Two elementary band representation model, Fermi surface nesting, and surface topological superconductivity in $A$ V $_{3}$ Sb $_{5}$ ( $A = K, Rb, Cs$ )

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