Superconductivity with Rashba Spin-Orbit Coupling and Magnetic Field

TL;DR

This paper explores how Rashba spin-orbit coupling and magnetic fields influence superconductivity at oxide interfaces, revealing complex pairing states and phase diagrams relevant to LaAlO3-SrTiO3 systems.

Contribution

It introduces a microscopic pairing model that captures both inter-band and intra-band superconducting states influenced by SOC and magnetic fields.

Findings

Identification of asymmetric Fermi surfaces due to SOC and magnetism

Derivation of phase diagram for different superconducting states

Analysis of density of states for various phases

Abstract

Two dimensional electron systems at oxide interfaces are often influenced by a Rashba type spin- orbit coupling (SOC), which is tunable by a transverse electric field. Ferromagnetism at the interface can simultaneously induce strong local magnetic fields. This combination of SOC and magnetism leads to asymmetric two-sheeted Fermi surfaces, on which either intra- or inter-band pairing is favored. The superconducting order parameters are derived within a microscopic pairing model realizing both, the Bardeen-Cooper-Schrieffer superconductor with inter-band pairing in the regime of dominating magnetic field, and a mixed-parity intra-band pairing state with finite-momentum pairing in the regime of dominating SOC. We present a phase diagram for the superconducting groundstates and analyze the density of states of the different phases. The results are discussed in the context of superconductivity and ferromagnetism at LaAlO3-SrTiO3 interfaces.