Search for plasmons in isotropic Luttinger semimetals

TL;DR

This study explores the conditions under which thermal plasmons emerge in isotropic Luttinger semimetals at finite temperatures, providing insights into their properties and potential experimental detection.

Contribution

It is the first detailed analysis of plasmon behavior in Luttinger semimetals at various temperatures, highlighting the role of temperature and material parameters.

Findings

Thermal plasmons appear at nonzero temperatures but not at zero temperature.

The lifetime of plasmons depends on temperature, effective mass, and interaction strength.

Inelastic scattering rates show sharp peaks indicating QBCP signatures.

Abstract

Luttinger semimetals include materials like gray tin ($\alpha$-Sn) and mercury telluride, which are three-dimensional gapless semiconductors having a quadratic band crossing point (QBCP). Due to a growing interest in QBCPs and new experimental efforts, it is essential to study the finite-temperature properties of such systems. In this paper, we investigate the emergence of plasmons in the presence of Coulomb interactions in isotropic Luttinger semimetals, for zero as well as generic nonzero temperatures. When the Fermi level lies right at the QBCP, which is the point where twofold degenerate conduction and valence bands touch each other quadratically, we find that plasmons cannot appear at zero temperature. However, for nonzero temperatures, thermal plasmons are generated. Whether they are long-lived or not depends on the values of temperature, effective electron mass and effective fine-structure constant, and the number of fermion flavors. We also numerically estimate the behavior of the inelastic scattering rate at nonzero temperatures, as a function of energy, where the signatures of the QBCP thermal plasmons show up as a sharp peak. Our results will thus serve as a guide to experimental probes on these systems.