Thermal Hall Conductivity in Superconducting Phase on Kagome Lattice

TL;DR

This study explores how spin-orbit coupling influences pairing symmetry and thermal Hall conductivity in superconducting states on a kagome lattice, revealing topological phases and their temperature-dependent behaviors.

Contribution

It demonstrates the emergence of topological superconducting states induced by spin-orbit coupling on the kagome lattice and analyzes their thermal Hall responses.

Findings

Spin-orbit coupling induces a topological superconducting state.

Thermal Hall conductivity reflects the topological nature of the superconducting phase.

Pairing symmetry is highly sensitive to spin-orbit coupling and interaction amplitudes.

Abstract

Motivated by a previous "$sd^2$-graphene" study, the pairing symmetry in the superconducting state and the thermal Hall conductivity are investigated by a self-consistent Bogoliubov--de Gennes approach on the kagome lattice with intrinsic spin-orbit coupling near van Hove fillings. While the topologically trivial state with broken time-reversal symmetry appears in the absence of spin-orbit coupling, the highest flat band becomes dispersive with a hexagonal symmetry due to spin-orbit coupling, which leads to a topological superconducting state. Since the thermal Hall conductivity in the low-temperature limit is associated with the topological property of time-reversal symmetry breaking superconductors, we study its temperature dependence near van Hove fillings. In particular, the pairing symmetry in the highest flat band is sensitive to the amplitudes of spin-orbit coupling and the attractive interaction, which is reflected remarkably in the thermal Hall conductivity. The obtained result may enable us to investigate the stable superconducting state on the kagome lattice.