Strong-coupling and the Stripe phase of $^3$He

TL;DR

This paper investigates the stability of the stripe phase in thin films of superfluid $^3$He using a strong-coupling Ginzburg-Landau theory, revealing its stability over a wide range of conditions despite being less stable than the A phase.

Contribution

It introduces a strong-coupling Ginzburg-Landau approach to analyze the phase diagram of superfluid $^3$He in thin films, providing new insights into the stability of the stripe phase.

Findings

Stripe phase is stable over a large parameter range.

Stability of the Stripe phase is reduced compared to the A phase.

The approach accurately reproduces the bulk superfluid phase diagram.

Abstract

Thin films of superfluid $^3$He were predicted, based on weak-coupling BCS theory, to have a stable phase which spontaneously breaks translational symmetry in the plane of the film. This crystalline superfluid, or "stripe" phase, develops as a one dimensional periodic array of domain walls separating degenerate B phase domains. We report calculations of the phases and phase diagram for superfluid $^3$He in thin films using a strong-coupling Ginzburg-Landau theory that accurately reproduces the bulk $^3$He superfluid phase diagram. We find that the stability of the Stripe phase is diminished relative to the A phase, but the Stripe phase is stable in a large range of temperatures, pressures, confinement, and surface conditions.