Spin, orbital, Weyl and other glasses in topological superfluids

TL;DR

This paper explores various topological glass states in superfluid helium-3 confined in nanostructures, highlighting their complex textures, topological charges, and the interplay between real-space and momentum-space topologies.

Contribution

It introduces the concept of multiple topological glass states in superfluid helium-3 and characterizes their textures and topological invariants in disordered environments.

Findings

Identification of skyrmion, spin vortex, and hopfion glasses in superfluid helium-3.

Observation of randomly distributed topological invariants in momentum space.

Demonstration of connections between real-space and momentum-space topologies in these glasses.

Abstract

One of the most spectacular discoveries made in superfluid $^3$He confined in a nanostructured material like aerogel or nafen was the observation of the destruction of the long-range orientational order by a weak random anisotropy. The quenched random anisotropy provided by the confining material strands produces several different glass states resolved in NMR experiments in the chiral superfluid $^3$He-A and in the time-reversal-invariant polar phase. The smooth textures of spin and orbital order parameters in these glasses can be characterized in terms of the randomly distributed topological charges, which describe skyrmions, spin vortices and hopfions. In addition, in these skyrmion glasses the momentum-space topological invariants are randomly distributed in space. The Chern mosaic, Weyl glass, torsion glass and other exotic topological sates are examples of close connections between the real-space and momentum-space topologies in superfluid $^3$He phases in aerogel.