Temperature-Dependent Collective Excitations in a Three-Dimensional Dirac System ZrTe$_{5}$

TL;DR

This study investigates temperature-dependent collective excitations in ZrTe$_{5}$, revealing unique plasmon behavior in 3D Dirac systems and linking it to the material's resistivity anomaly.

Contribution

The paper provides experimental evidence of plasmon behavior in ZrTe$_{5}$ and connects it to the topological properties and resistivity anomaly of the material.

Findings

Plasmon energy scales with the one-third power of carrier density.

The resistivity anomaly is linked to temperature-induced chemical potential shifts.

Unique plasmon behavior confirms the 3D Dirac nature of ZrTe$_{5}$.

Abstract

Zirconium pentatelluride (ZrTe$_{5}$), a system with a Dirac linear band across the Fermi level and anomalous transport features, has attracted considerable research interest for it is predicted to be located at the boundary between strong and weak topological insulators separated by a topological semimetal phase. However, the experimental verification of the topological phase transition and the topological ground state in ZrTe$_{5}$ is full of controversies, mostly due to the difficulty of precisely capturing the small gap evolution with single-particle band structure measurements. Alternatively, the collective excitations of electric charges, known as plasmons, in Dirac systems exhibiting unique behavior, can well reflect the topological nature of the band structure. Here, using reflective high-resolution electron energy loss spectroscopy (HREELS), we investigate the temperature-dependent collective excitations of ZrTe$_{5}$, and discover that the plasmon energy in ZrTe$_{5}$ is proportional to the $1/3$ power of the carrier density $n$, which is a unique feature of plasmons in three-dimensional Dirac systems. Based on this conclusion, the origin of the resistivity anomaly of ZrTe$_{5}$ can be attributed to the temperature-dependent chemical potential shift in extrinsic Dirac semimetals.