Colossal orbital-Edelstein effect in non-centrosymmetric superconductors

TL;DR

This paper reveals a colossal orbital Edelstein effect in non-centrosymmetric superconductors, where supercurrent induces a significantly larger orbital magnetization than spin magnetization, with tunable sign and potential for detection.

Contribution

It demonstrates that orbital magnetization dominates over spin in Edelstein effects in non-centrosymmetric superconductors, a novel insight into magneto-electric phenomena.

Findings

Orbital magnetization exceeds spin magnetization by over an order of magnitude.

Sign of orbital magnetization can be tuned by Fermi level positioning.

Orbital Edelstein effect persists at edges and is robust to order parameter inhomogeneities.

Abstract

In superconductors that lack inversion symmetry, the flow of supercurrent can induce a non-vanishing magnetization, a phenomenon which is at the heart of non-dissipative magneto-electric effects, also known as Edelstein effects. For electrons carrying spin and orbital moments a question of fundamental relevance deals with the orbital nature of magneto-electric effects in conventional spin-singlet superconductors with Rashba coupling. Remarkably, we find that the supercurrent-induced orbital magnetization is more than one order of magnitude greater than that due to the spin, giving rise to a colossal magneto-electric effect. The induced orbital magnetization is shown to be sign tunable, with the sign change occurring for the Fermi level lying in proximity of avoiding crossing points in the Brillouin zone. In the presence of superconducting phase inhomogeneities, a modulation of the Edelstein signal on the scale of the superconducting coherence length appears, leading to domains with opposite orbital moment orientations. These hallmarks are robust to real-space self-consistent treatment of the superconducting order parameter. The orbital-dominated magneto-electric phenomena, hence, have clear-cut marks for detection both in the bulk and at the edge of the system and are expected to be a general feature of multi-orbital superconductors with inversion symmetry breaking.