TY - JOUR

T1 - Superconductivity from repulsive interactions on the kagome lattice

AU - Romer, Astrid T.

AU - Bhattacharyya, Shinibali

AU - Valenti, Roser

AU - Christensen, Morten H.

AU - Andersen, Brian M.

PY - 2022/11/23

Y1 - 2022/11/23

N2 - The discovery of superconductivity in layered vanadium-based kagome metals AV3Sb5 (A: K, Rb, Cs) has added a new family of materials to the growing class of possible unconventional superconductors. However, the nature of the superconducting pairing in these materials remains elusive. We present a microscopic theoretical study of the leading superconducting instabilities on the kagome lattice based on spin-and charge-fluctuation mediated Cooper pairing. The applied methodology includes effects of both on-site and nearest-neighbor repul-sive Coulomb interactions. Near the upper van Hove filling-relevant for the AV3Sb5 materials-we find a rich phase diagram with several pairing symmetries being nearly degenerate. In particular, while a substantial fraction of the phase diagram is occupied by a spin-singlet order parameter transforming as a two-dimensional irreducible representation of the point group, several nodal spin-triplet pairing states remain competitive. We compute the band and interaction parameter dependence of the hierarchy of the leading superconducting instabilities and determine the detailed momentum dependence of the resulting preferred gap structures. Crucially, for moderate values of the interaction parameters, the individual pairing states depend strongly on momentum and exhibit multiple nodes on the Fermi surface. We discuss the properties of these superconducting gap structures in light of recent experimental developments of the AV3Sb5 materials.

AB - The discovery of superconductivity in layered vanadium-based kagome metals AV3Sb5 (A: K, Rb, Cs) has added a new family of materials to the growing class of possible unconventional superconductors. However, the nature of the superconducting pairing in these materials remains elusive. We present a microscopic theoretical study of the leading superconducting instabilities on the kagome lattice based on spin-and charge-fluctuation mediated Cooper pairing. The applied methodology includes effects of both on-site and nearest-neighbor repul-sive Coulomb interactions. Near the upper van Hove filling-relevant for the AV3Sb5 materials-we find a rich phase diagram with several pairing symmetries being nearly degenerate. In particular, while a substantial fraction of the phase diagram is occupied by a spin-singlet order parameter transforming as a two-dimensional irreducible representation of the point group, several nodal spin-triplet pairing states remain competitive. We compute the band and interaction parameter dependence of the hierarchy of the leading superconducting instabilities and determine the detailed momentum dependence of the resulting preferred gap structures. Crucially, for moderate values of the interaction parameters, the individual pairing states depend strongly on momentum and exhibit multiple nodes on the Fermi surface. We discuss the properties of these superconducting gap structures in light of recent experimental developments of the AV3Sb5 materials.

KW - GAP ANISOTROPY

KW - CHARGE ORDER

KW - SYMMETRY

KW - BREAKING

U2 - 10.1103/PhysRevB.106.174514

DO - 10.1103/PhysRevB.106.174514

M3 - Journal article

VL - 106

JO - Physical Review B

JF - Physical Review B

SN - 2469-9950

IS - 17

M1 - 174514

ER -