Zero-temperature dynamics of solid 4He from quantum Monte Carlo simulations

TL;DR

This paper uses quantum Monte Carlo simulations to analyze the zero-temperature lattice dynamics of solid helium-4, revealing detailed phonon dispersion and insights into quasiparticle coherence across different densities.

Contribution

It provides the first comprehensive phonon dispersion relations for solid 4He at zero temperature using quantum Monte Carlo methods, including optic and acoustic branches.

Findings

Complete phonon dispersion obtained for solid 4He

Identification of transverse phonon modes

Insights into quasiparticle coherence in intermediate momentum region

Abstract

The lattice dynamics of hcp crystalline 4He is studied at zero temperature and for two different densities (near and far from melting), using a ground-state path-integral quantum Monte Carlo technique. The complete phonon dispersion is obtained, with particular attention to the separation of optic and acoustic branches and to the identification of transverse modes. Our study also sheds light onto the residual coherence affecting quasiparticle excitations in the intermediate momentum region, in-between the phonon and nearly-free particle regimes.