Superconductivity with Rashba Spin-Orbit Coupling and Magnetic Field

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.