Roton excitation in overpressurized superfluid He-4

TL;DR

This paper uses quantum Monte Carlo simulations to study overpressurized superfluid helium-4, focusing on structural, superfluid properties, and the roton excitation energy, identifying the pressure where superfluidity becomes unstable.

Contribution

It provides a theoretical analysis of overpressurized superfluid He-4, estimating the roton energy vanishing point and the spinodal density using advanced simulation techniques.

Findings

Roton energy vanishes at about 100 bars pressure.

Identified the spinodal density as the upper limit for metastable superfluid phase.

Provided structural and superfluid property estimates across densities.

Abstract

We carry out a theoretical investigation of overpressurized superfluid phases of He-4 by means of quantum Monte Carlo (QMC) simulations. As a function of density, we study structural and superfluid properties, and estimate the energy of the roton excitation by inverting imaginary-time density correlation functions computed by QMC, using Maximum Entropy. We estimate the pressure at which the roton energy vanishes to be about 100 bars, which we identify with the spinodal density, i.e., the upper limit for the existence of a metastable superfluid phase.