Detection of topological phase transitions through entropy measurements: the case of germanene

TL;DR

This paper introduces a method to detect topological phase transitions in materials like germanene by analyzing entropy per electron features, providing a new experimental fingerprint for such transitions.

Contribution

It demonstrates that entropy per electron measurements can serve as a fingerprint for topological phase transitions, supported by first-principles calculations in germanene.

Findings

Resonant entropy features indicate topological transitions.

Strong entropy spikes occur at low temperatures near transition points.

Van Hove singularities appear as zeros in entropy dependence.

Abstract

We propose a characterization tool for studies of the band structure of new materials promising for the observation of topological phase transitions. We show that a specific resonant feature in the entropy per electron dependence on the chemical potential may be considered as a fingerprint of the transition between topological and trivial insulator phases. The entropy per electron in a honeycomb two-dimensional crystal of germanene subjected to the external electric field is obtained from the first principle calculation of the density of electronic states and the Maxwell relation. We demonstrate that, in agreement to the recent prediction of the analytical model, strong spikes in the entropy per particle dependence on the chemical potential appear at low temperatures. They are observed at the values of the applied bias both below and above the critical value that corresponds to the transition between the topological insulator and trivial insulator phases, while the giant resonant feature in the vicinity of zero chemical potential is strongly suppressed at the topological transition point, in the low temperature limit. In a wide energy range, the van Hove singularities in the electronic density of states manifest themselves as zeros in the entropy per particle dependence on the chemical potential.