Effective Lagrangian and Topological Interactions in Supersolids

TL;DR

A low-energy effective Lagrangian describing zero temperature supersolids is constructed and a topological term in the lagrangian that couples superfluid and crystalline modes is identified that is dominant in problems involving defects.

Abstract

We construct a low-energy effective Lagrangian describing zero-temperature supersolids. Galilean invariance imposes strict constraints on the form of the effective Lagrangian. We identify a topological term in the Lagrangian that couples superfluid and crystalline modes. For small superfluid fractions this interaction term is dominant in problems involving defects. As an illustration, we compute the differential cross section of scatterings of low-energy transverse elastic phonons by a superfluid vortex. The result is model-independent.

Figures (1)

• Figure 1: The scattering of transverse elastic phonons by a superfluid vortex.