Dirac Polarons and Resistivity Anomaly in ZrTe5 and HfTe5

TL;DR

This paper proposes a theory of Dirac polarons to explain the resistivity peak and anomalous transport behaviors in ZrTe5 and HfTe5, linking temperature-induced chemical potential shifts to topological band structure effects.

Contribution

It introduces the concept of Dirac polarons composed of Dirac electrons and phonons, providing a novel explanation for resistivity anomalies in transition-metal pentatellurides.

Findings

Dirac polarons cause the resistivity peak at finite temperatures.

Formation of neutral Dirac polarons explains anomalous electric and thermoelectric behaviors.

Temperature-driven chemical potential shifts modulate the topological band gap.

Abstract

Resistivity anomaly, a sharp peak of resistivity at finite temperatures, in the transition-metal pentatellurides ZrTe5 and HfTe5 was observed four decades ago, and more exotic and anomalous behaviors of electric and thermoelectric transport were revealed recent years. Here we present a theory of Dirac polarons, composed by massive Dirac electrons and holes in an encircling cloud of lattice displacements or phonons at finite temperatures. The chemical potential of Dirac polarons sweeps the band gap of the topological band structure by increasing the temperature, leading to the resistivity anomaly. Formation of a nearly neutral state of Dirac polarons accounts for the anomalous behaviors of the electric and thermoelectric resistivity.