Magneto-optics of a Weyl semimetal beyond the conical band approximation: the case study of TaP

TL;DR

This paper investigates unusual Landau-level transitions in the Weyl semimetal TaP, revealing complex band structure effects beyond the simple conical approximation, and proposes a theoretical model to explain these phenomena.

Contribution

It introduces a new theoretical model for electronic bands in Weyl semimetals that accounts for complex Landau-level transitions observed experimentally.

Findings

Unusual Landau-level transitions decreasing with magnetic field in TaP

Transitions explained by a partially gapped nodal-loop in the band structure

Theoretical model successfully captures magneto-optical data

Abstract

Landau-level spectroscopy, the optical analysis of electrons in materials subject to a strong magnetic field, is a versatile probe of the electronic band structure and has been successfully used in the identification of novel states of matter such as Dirac electrons, topological materials or Weyl semimetals. The latter arise from a complex interplay between crystal symmetry, spin-orbit interaction and inverse ordering of electronic bands. Here, we report on unusual Landau-level transitions in the monopnictide TaP that decrease in energy with increasing magnetic field. We show that these transitions arise naturally at intermediate energies in time-reversal-invariant Weyl semimetals where the Weyl nodes are formed by a partially gapped nodal-loop in the band structure. We propose a simple theoretical model for electronic bands in these Weyl materials that captures the collected magneto-optical data to great extent.