Finite Temperature Properties of a Supersolid: a RPA Approach

TL;DR

This paper investigates the finite temperature properties of a supersolid phase in helium-4 using a RPA approach, revealing constant vacancy density and matching experimental specific heat jumps.

Contribution

It provides a detailed RPA analysis of supersolid helium-4, emphasizing the role of vacancies and challenging thermal activation assumptions.

Findings

Vacancy density remains constant with temperature.

Calculated specific heat jump aligns with experiments.

Supports vacancies' importance in supersolid behavior.

Abstract

We study in random-phase approximation the newly discovered supersolid phase of ${}^4$He and present in detail its finite temperature properties. ${}^4$He is described within a hard-core quantum lattice gas model, with nearest and next-nearest neighbour interactions taken into account. We rigorously calculate all pair correlation functions in a cumulant decoupling scheme. Our results support the importance of the vacancies in the supersolid phase. We show that in a supersolid the net vacancy density remains constant as function of temperature, contrary to the thermal activation theory. We also analyzed in detail the thermodynamic properties of a supersolid, calculated the jump in the specific heat which compares well to the recent experiments.