Magneto-optical probe of the fully gapped Dirac band in ZrSiS

TL;DR

This study uses far-infrared magneto-optical measurements to investigate the gapped Dirac band in ZrSiS, revealing field-dependent intra- and interband transitions consistent with a simple 2D Dirac model with a small gap.

Contribution

It provides the first magneto-optical characterization of the gapped Dirac bands in ZrSiS, demonstrating the field dependence of intra- and interband transitions within a simple 2D Dirac framework.

Findings

Field-dependent features follow a B dependence, consistent with a 2D Dirac model.

Identified a field-independent spectral feature, with potential origins discussed.

Estimated a small gap of 26 meV and Fermi velocity of 3^5 m/s in ZrSiS.

Abstract

We present a far-infrared magneto-optical study of the gapped nodal-line semimetal ZrSiS in magnetic fields $B$ up to 7 T. The observed field-dependent features, which represent intra- (cyclotron resonance) and interband transitions, develop as $\sqrt{B}$ in increasing field and can be consistently explained within a simple 2D Dirac band model with a gap of 26 meV and an averaged Fermi velocity of $3\times10^{5}$ m/s. This indicates a rather narrow distribution of these parameters along the in-plane portions of the nodal line in the Brillouin zone. A field-induced feature with an energy position that does not depend on $B$ is also detected in the spectra. Possible origins of this feature are discussed.