Edge states of 2D time-reversal-invariant topological superconductors with strong interactions and disorder: A view from the lattice

TL;DR

This paper investigates how strong interactions and disorder affect the edge states of 2D time-reversal-invariant topological superconductors, revealing a stable infinite-randomness phase characterized by localized Majorana fermions at domain walls.

Contribution

It develops a strong-disorder renormalization group analysis showing the emergence of a stable infinite-randomness fixed point on the superconductor's edge under strong disorder and interactions.

Findings

Majorana fermions localize at domain walls

Infinite-randomness fixed point is stable with disorder and interactions

Time-reversal symmetry can be spontaneously broken

Abstract

Two-dimensional time-reversal-invariant topological superconductors host helical Majorana fermions at their boundary. We study the fate of these edge states under the combined influence of strong interactions and disorder, using the effective 1D lattice model for the edge introduced by Jones and Metlitski [Phys. Rev. B 104, 245130 (2021)]. We specifically develop a strong-disorder renormalization group analysis of the lattice model and identify a regime in which time-reversal is broken spontaneously, creating random magnetic domains; Majorana fermions localize to domain walls and form an infinite-randomness fixed point, identical to that appearing in the random transverse-field Ising model. While this infinite-randomness fixed point describes a fine-tuned critical point in a purely 1D system, in our edge context there is no obvious time-reversal-preserving perturbation that destabilizes the fixed point. Our analysis thus suggests that the infinite-randomness fixed point emerges as a stable phase on the edge of 2D topological superconductors when strong disorder and interactions are present.