Tuning electronic pairing by uniaxial strain in kagome lattices

TL;DR

This paper explores how uniaxial strain influences electronic pairing and topological phases in kagome lattices, revealing strain-controlled phase transitions, coexistence of superconductivity and charge density waves, and the interplay of interactions and topology.

Contribution

It introduces a comprehensive mean-field analysis of strained kagome lattices, demonstrating strain-induced topological and superconducting phases, and the coexistence of these states under specific conditions.

Findings

Uniaxial strain induces a nematic charge density wave in kagome lattices.

Moderate strain enables coexistence of superconductivity and charge density waves.

Topological phase transitions are driven by interaction strength and strain.

Abstract

We study the interplay of attractive electron interactions and topological states in strained kagome lattices with spin-orbit coupling via a Hubbard Hamiltonian in the mean-field approximation. In the unstrained lattice, there is a topological phase transition from a quantum spin Hall state to a charge density wave (CDW) with increasing interaction strength. Upon applying a uniform uniaxial strain to the lattice, we find a new phase with coexisting CDWs and topological states. For increasing interaction strength or strain, the system is driven into a pure CDW, signaling topological phase transitions. The directionality (nematicity) of the CDW is controlled by the direction of the applied strain. When $s$ wave electronic pairing is allowed, the system develops a superconducting order beyond a threshold attraction, which is totally suppressed by the onset of a CDW with increasing interaction. Most interestingly, moderate strain allows the coexistence of superconductivity and CDWs for a range of interaction values. This illustrates how electronic interactions and single-particle topological structures compete to create unusual correlated phases in kagome systems.