A Wave Function Describing Superfluidity in a Perfect Crystal

TL;DR

This paper introduces a new many-body wave function that models supersolid behavior in perfect crystals, capturing both superfluidity and crystalline order, and predicts observable non-classical rotational inertia.

Contribution

It presents a novel wave function incorporating short-range correlations that demonstrates supersolid properties in perfect crystals, linking theory with recent experimental findings.

Findings

Superfluid fraction can reach about 1% in certain conditions

Wave function exhibits both diagonal and off-diagonal long-range order

Predicts non-classical rotational inertia in perfect crystals

Abstract

We propose a many-body wave function that exhibits both diagonal and off-diagonal long-range order. Incorporating short-range correlations due to interatomic repulsion, this wave function is shown to allow condensation of zero-point lattice vibrations and phase rigidity. In the presence of an external velocity field, such a perfect crystal will develop non-classical rotational inertia, exhibiting the supersolid behavior. In a sample calculation we show that the superfluid fraction in this state can be as large as of order 0.01 in a reasonable range of microscopic parameters. The relevance to the recent experimental evidence of a supersolid state by Chan and Kim is discussed.