Elementary excitations in a supersolid

TL;DR

This paper investigates the low-energy excitations in a supersolid, revealing coupled longitudinal modes and unchanged transverse modes, with experimental signatures proposed for these novel excitations.

Contribution

It introduces the coupling between lattice vibrations and superfluid modes, leading to distinct excitation branches in a supersolid, and predicts experimental signatures.

Findings

Two coupled longitudinal modes in supersolids

Transverse modes remain unchanged from normal solids

Experimental signatures include specific heat and density correlations

Abstract

We study elementary low energy excitations inside a supersolid. We find that the coupling between the longitudinal lattice vibration mode and the superfluid mode leads to two longitudinal modes (one upper branch and one lower branch) inside the supersolid, while the transverse modes in the supersolid stay the same as those inside a normal solid. We also work out various experimental signatures of these novel elementary excitations by evaluating the Debye-Waller factor, density-density correlation, vortex loop-vertex loop interactions, specific heat and excess entropy from the vacancies per mole.