Abnormal behavior of crystalline methane in temperature interval $60-70~K$. From experiment to theory

TL;DR

This paper investigates anomalies in the properties of solid methane between 60-70 K, proposing a new concept of 'topons' to explain collective rotational excitations and their effects on the material's behavior.

Contribution

It introduces the concept of 'topons' to explain the observed anomalies in solid methane's properties at specific temperatures, linking experimental observations with theoretical interpretation.

Findings

Anomalies observed in mechanical, structural, and spectral properties at 60-70 K.

The 'topons' concept explains collective rotational excitations in solid methane.

The anomalies are consistent with the proposed quantum collective excitations.

Abstract

The paper presents an analysis of mechanical, structural, thermophysical and spectral properties of solid methane in temperature interval $0.5T_{tr} -T_{tr}$ ($T_{tr}$ is the triple point temperature) under equilibrium vapor pressure. It is shown that the anomalies of the studied properties at temperatures 60--70~K have been observed in the body of the reviewed papers. A concept of "topons" (collective excitations of rotational degrees of freedom in solid methane) is proposed. A whole of the observed anomalies can be explained in the frames of this concept. Key words: solid methane, quantum crystals, rotational degrees of freedom, thermophysical and mechanical properties of the crystals