Magneto-optic signatures in the gapped Dirac semimetal with mixed linear and parabolic dispersions of ZrTe5

TL;DR

This study provides a theoretical analysis of Landau levels and magneto-optical conductivity in a gapped Dirac semimetal with mixed dispersions, revealing magnetic field-driven topological phase transitions and signatures consistent with experiments.

Contribution

It offers a systematic theoretical framework explaining magneto-optical signatures and topological phase changes in ZrTe$_5$ under magnetic fields, extending prior experimental observations.

Findings

Strong magnetic fields induce a transition from topological insulator to trivial insulator in ZrTe$_5$.

Distinct signatures in density of states and conductivity are observed across different magnetic field regimes.

Weak magnetic fields show a specific relation in conductivity peaks that matches experimental data.

Abstract

In this paper, we give a systematic theoretical study on the Landau levels (LLs) and magneto-optical conductivity Re$(\sigma_{\alpha\alpha})$ in a gapped Dirac semimetal model with mixed linear and parabolic dispersions under a magnetic field, which was recently proposed by Jiang \textit{et al.} [Phys. Rev. Lett. {\bf125}, 046403 (2020)] to explain the experimental magnetoinfrared spectroscopy in the three-dimensional ZrTe$_5$ crystal. We find that the strong magnetic field can drive the LLs become noninverted and thus the strong topological insulator phase in ZrTe$_5$ turns to be a trivial insulator. In the different magnetic field regions, the density of states and Re$(\sigma_{\alpha\alpha})$ can exhibit distinct signatures. Moreover, when the magnetic field is weak, a qualitative relation in Re$(\sigma_{zz})$ between the peaks at the saddle points is revealed as Re$(\sigma_{zz}^{\zeta_n})>$Re$(\sigma_{zz}^\Gamma)$, which is in good agreement with the experiment.