An explanation for the glass-like anomaly in the low-temperature specific heat of incommensurate phases

TL;DR

This paper explains the glass-like anomaly in the low-temperature specific heat of incommensurate phases by considering phason damping effects, aligning theoretical scenarios with experimental data.

Contribution

It introduces a comprehensive explanation for the anomaly by analyzing three phason dynamics scenarios and matching them with experimental observations.

Findings

Phason damping is crucial for explaining specific heat anomalies.

Different phason gap scenarios correspond to different materials.

Theoretical estimates agree with experimental data.

Abstract

An explanation for the glass-like anomaly observed in the low-temperature specific heat of incommensurate phases is proposed. The key point of this explanation is the proper account for the phason damping when computing the thermodynamic magnitudes. The low-temperature specific heat of the incommensurate phases is discussed within three possible scenarios for the phason dynamics: no phason gap, static phason gap and a phason gap of dynamical origin. Existing NMR and inelastic scattering data indicate that these scenarios are possible in biphenyl, blue bronze $\rm K_{0.30}MoO_3$ and BCPS respectively. Estimates of the corresponding low-temperature specific heat are in reasonable agreement with the experiments.