Generation Efficiencies for Propagating Modes in a Supersolid

TL;DR

This paper analyzes the propagation and generation efficiencies of modes in a supersolid using hydrodynamics, highlighting differences from previous models and the effectiveness of heaters and transducers.

Contribution

It introduces a comprehensive theory including both lattice and internal pressure stresses, improving understanding of mode propagation and generation in supersolids.

Findings

Transducers are more efficient at generating elastic waves.

Heaters are more efficient at producing fourth sound waves.

The theory applies to isotropic systems like glassy or polycrystalline helium.

Abstract

Using Andreev and Lifshitz's supersolid hydrodynamics, we obtain the propagating longitudinal modes at non-zero applied pressure $P_{a}$ (necessary for solid 4He), and their generation efficiencies by heaters and transducers. For small $P_{a}$, a solid develops an internal pressure $P \sim P_{a}^2$. This theory has stress contributions both from the lattice and an internal pressure $P$. Because both types of stress are included, the normal mode analysis differs from previous works. Not surprisingly, transducers are significantly more efficient at producing elastic waves and heaters are significantly more efficient at producing fourth sound waves. We take the system to be isotropic, which should apply to systems that are glassy or consist of many crystallites; the results should also apply, at least qualitatively, to single-crystal hcp 4He.