Hybridization of localized and density modes for the roton spectrum of superfluid ${^4}$He

TL;DR

This paper introduces a hybrid model combining density and localized vortex-core modes to better describe the roton spectrum of superfluid helium-4, aligning theoretical predictions with experimental observations.

Contribution

It proposes a novel hybridization approach that incorporates localized vortex-core modes alongside density excitations, providing a more comprehensive description of the roton spectrum.

Findings

The hybrid model matches experimental structure factor data.

The model predicts vortex loop excitations consistent with Raman scattering.

Energy estimates agree with critical velocity measurements.

Abstract

A new description is presented for the roton part of the energy spectrum of supe rfluid ${^4}$He. It is based on the assumption that in addition to the Feynman density excitations, there exist localized modes which describe vortex-core elements. The energy spectrum which results from the hybridization of these two kinds of excitations is compared to the experimental data namely the structure factor and the scattering cross-section for the single quasiparticle excitation. Another type of excitation interpreted as a vortex loop is obtained whose energy agrees both with Raman scattering and critical velocity experiments.