Relations between normal state nonreciprocal transport and the superconducting diode effect in the trivial and topological phases

TL;DR

This paper explores how nonreciprocal transport effects in normal and superconducting states are influenced by system topology, especially in nanowires, revealing the connection between nonreciprocal phenomena and topological phases.

Contribution

It provides analytic expressions linking normal state rectification and superconducting diode effects, highlighting the impact of topology on nonreciprocal transport in nanowire systems.

Findings

Topology significantly alters nonreciprocal transport properties.

Analytic formulas connect normal and superconducting nonreciprocal effects.

Nonreciprocal effects serve as indicators of topological phases.

Abstract

Nonreciprocal transport effects can occur in the normal state of conductors and in superconductors when both inversion and time-reversal symmetry are broken. Here, we consider systems where magnetochiral anisotropy (MCA) of the energy spectrum due to an externally applied magnetic field results in a rectification effect in the normal state and a superconducting (SC) diode effect when the system is proximitised by a superconductor. Focussing on nanowire systems, we obtain analytic expressions for both normal state rectification and SC diode effects that reveal the commonalities - as well as differences - between these two phenomena. Furthermore, we consider the nanowire brought into an (almost) helical state in the normal phase or a topological superconducting phase when proximitised. In both cases this reveals that the topology of the system considerably modifies its nonreciprocal transport properties. Our results provide new insights into how to determine the origin of nonreciprocal effects and further evince the strong connection of nonreciprocal transport with the topological properties of a system.