Elementary excitations and heat capacity singularity in superfluid helium

TL;DR

This paper proposes a new type of elementary excitation called helons in superfluid helium, explaining the heat capacity singularity near the phase transition by generalizing Landau's theory to include temperature-dependent spectra.

Contribution

It introduces helons as a novel elementary excitation in superfluid helium, extending Landau's theory to account for temperature-dependent spectra and heat capacity anomalies.

Findings

Identification of helons as additional excitations in superfluid helium

Temperature dependence of excitation spectra explains heat capacity singularity

Supports the generalized Landau superfluidity criterion

Abstract

We proceed from the premise that the spectrum of elementary excitations in the normal component in Landau's theory of superfluidity should depend on the superfluid helium temperature. This leads to generalization of the Landau superfluidity criterion. On this basis, taking into account available experimental data on inelastic neutron scattering, it is shown that, in addition to phonon--roton excitations, there is one more type of elementary excitations in superfluid helium, which we called helons. The energy spectrum with such a momentum dependence was first proposed by Landau. The helon energy spectrum shape and its temperature dependence make it possible to explain the singular behavior of the heat capacity of superfluid helium near its phase transition to the normal state.