Strongly parity-mixed superconductivity in Rashba-Hubbard model

TL;DR

This study investigates superconductivity in the Rashba-Hubbard model, revealing a robust, strongly parity-mixed superconducting phase influenced by magnetic fluctuations and van Hove singularities, with implications for topological and nonreciprocal transport.

Contribution

It employs fluctuation-exchange approximation to analyze superconductivity in the Rashba-Hubbard model, highlighting the coexistence of dominant d-wave and subdominant triplet pairings across a wide filling range.

Findings

Identification of a strongly parity-mixed superconducting phase.

Demonstration of magnetic fluctuation effects on superconductivity.

Analysis of van Hove singularity impacts on pairing symmetry.

Abstract

Heterostructures containing strongly correlated electron systems provide a platform to clarify interplay of electron correlation and Rashba spin-orbit coupling in unconventional superconductors. Motivated by recent fabrication of artificially-engineered heavy fermion superlattices and high-temperature cuprate superconductors, we conduct a thorough study on superconductivity in Rashba-Hubbard model. In contrast to previous weak coupling approaches, we employ fluctuation-exchange approximation to describe quantum critical magnetic fluctuations and resulting superconductivity. As a result, robust Fermi surfaces against magnetic fluctuations, incommensurate spin fluctuations, and a strongly parity-mixed superconducting phase are demonstrated in a wide range of electron filling from type-II van Hove singularity to half-filling. We also clarify impacts of type-II van Hove singularity on magnetic fluctuations and superconductivity. Whereas the $d_{x^2-y^2}$-wave pairing always dominant, subdominant spin-triplet pairing with either $p$-wave or $f$-wave symmetry shows a comparable magnitude, especially near the type-II van Hove singularity. Our results resolve unsettled issues on strongly correlated Rashba systems and uncover candidate systems of nonreciprocal transport and topological superconductivity.