Anomalous anharmonicity in doped cuprate superconductors

TL;DR

This paper investigates how Lifshitz transitions influence the nonlinear elastic properties of doped cuprate superconductors, highlighting the importance of electronic effects near Van Hove singularities and their impact on anharmonic constants.

Contribution

It reveals the significant role of electronic contributions to elastic properties near Lifshitz transitions in cuprates, especially around Van Hove singularities, and analyzes the behavior of the Grueneisen coefficient.

Findings

Electronic contributions become prominent near the Lifshitz transition.

An enhancement factor for anharmonic constants is derived.

Behavior of the Grueneisen coefficient near the transition is analyzed.

Abstract

Strong nonlinear elastic effects arise due to the Lifshitz transition associated with a change in the Fermi surface topology. It is shown that an electronic contribution to the elastic characteristics of cuprates becomes important if the chemical potential is near but not too near the Van Hove critical energy $\epsilon_c$. In the case of a saddle point singularity in the energy spectrum an enhancement factor arises for the "electronic" anharmonic constants of the 3rd and 4th order, that is proportional to $\epsilon_F/(\epsilon_F-\epsilon_c)$ to the 1st and 2nd power, respectively. The behaviour of the Grueneisen coefficient in the vicinity of the Lifshitz transition is considered.