Unconventional superconductivity protected from disorder on the kagome lattice

Abstract

Motivated by the recent discovery of superconductivity in the kagome AV3Sb5 (A=K, Rb, Cs) metals, we perform a theoretical study of the symmetry-allowed superconducting orders on the two-dimensional kagome lattice with focus on their response to disorder. We uncover a qualitative difference between the robustness of intraband spin-singlet (even-parity) and spin-triplet (odd-parity) unconventional superconductivity to atomic-scale nonmagnetic disorder. Due to the particular sublattice character of the electronic states on the kagome lattice, disorder in spin-singlet superconducting phases is only weakly pair-breaking despite the fact that the gap structure features sign changes. By contrast, spin-triplet condensates remain fragile to disorder on the kagome lattice. We demonstrate these effects in terms of the absence of impurity bound states and an associated weak disorder-induced Tc suppression for spin-singlet order. We also discuss the consequences for quasiparticle interference and their inherent tendency for momentum-space anisotropy due to sublattice effects on the kagome lattice. For unconventional kagome superconductors, our results imply that any allowed spin-singlet order, including for example d+id-wave superconductivity, exhibits a disorder-response qualitatively similar to standard conventional s-wave superconductors.

Source-reported materials — not catalogue approval

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