Route to Topological Superconductivity via Magnetic Field Rotation

TL;DR

This paper proposes a method to realize topological superconductivity in 2D s-wave superconductors by rotating the magnetic field into the plane, overcoming the high field requirement and extending topological states.

Contribution

It introduces a novel approach of magnetic field rotation to achieve topological superconductivity in conventional 2D superconductors, supported by a three-band model for LaAlO_3/SrTiO_3 interfaces.

Findings

Topological state persists with in-plane magnetic field orientation.

Rotating magnetic field extends topological phase to lower fields.

Three-band model supports experimental realization.

Abstract

The verification of topological superconductivity has become a major experimental challenge. Apart from the very few spin-triplet superconductors with p-wave pairing symmetry, another candidate system is a conventional, two-dimensional (2D) s-wave superconductor in a magnetic field with a sufficiently strong Rashba spin-orbit coupling. Typically, the required magnetic field to convert the superconductor into a topologically non-trivial state is however by far larger than the upper critical field H_c2, which excludes its realization. In this article, we argue that this problem can be overcome by rotating the magnetic field into the superconducting plane. We explore the character of the superconducting state upon changing the strength and the orientation of the magnetic field and show that a topological state, established for a sufficiently strong out-of-plane magnetic field, indeed extends to an in-plane field orientation. We present a three-band model applicable to the superconducting interface between LaAlO_3 and SrTiO_3, which should fulfil the necessary conditions to realize a topological superconductor.