Topological superconducting phases and Josephson effect in curved time-reversal-invariant superconductors

TL;DR

This paper investigates how geometric deformations in curved, time-reversal-invariant topological superconductors influence their phases, localized modes, and Josephson effects, revealing tunable topological and transport properties via curvature manipulation.

Contribution

It introduces the impact of geometric curvature on topological phases, localized modes, and Josephson effects in time-reversal-invariant superconductors, highlighting new ways to control superconducting properties.

Findings

Curvature inhomogeneity induces localized eigenmodes in topological phases.

Geometric control enables tuning of Josephson critical current and phase transitions.

Curvature can generate $ ext{0-} ext{π}$ transitions and $ ext{φ}$-junction behavior.

Abstract

We consider a Rashba spin-orbit coupled nanowire with anisotropic spin-singlet superconducting pairing and time-reversal-invariant symmetry. We explore the evolution of the topological superconducting phases of this system due to geometric deformations for the representative case of a wire bent in a semielliptical shape. We find that when the system is in its topological superconducting phase, strong inhomogeneities in the profile curvature can produce a pair of localized eigenmodes, which can be attributed to a nonuniform topological phase. The curved geometric profile also allows to tune the spin correlations of the superconducting state via the induced inhomogeneity of the spin-orbit coupling (SOC). The geometric control of the superconducting pair correlations allows to manipulate the critical current in Josephson junctions made up of two time reversal invariant topological superconductors separated by a spin-orbit coupled normal metal. In particular, we find that the curvature inhomogeneity can be exploited for amplifying the current intensity, but also to generate a $0-\pi$ transition, and a second harmonic contribution, which generates, for some specific geometric configurations, a $\varphi$-junction behavior.