Magneto-Optics of a Weyl Semimetal beyond the Conical Band Approximation: Case Study of TaP

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. arXiv:1912.07327v1 [cond-mat.mes-hall]

Nodal Semimetals: A Survey on Optical Conductivity

“…One can notice that there is a small bump on the initial linear at around 15 meV. This bump was reproduced in later optical measurements of TaAs; [ 92 ] a similar, but much stronger, peak was detected in TaP at comparable energies, [ 92,93 ] see Figure 7. In the study by Kimura et al [ 92 ] these features were attributed to the transitions between the Lifshitz points of the bands forming the Weyl nodes (Figure 1, middle row).…”

Optical Response of Chiral Multifold Semimetal PdGa

“…Even though the Fermi level in PdGa is much higher, we nonetheless find a nearly linear ridge in the optical spectrum and identify its origin, as discussed in the results. The combination with external stimuli, such as magnetic fields [43][44][45] or external pressure [46,47], which provide clean, non-invasive tuning mechanisms, makes the optical conductivity especially desirable in the search for topological materials.…”

Magneto-Optical Transport Properties of Type-II Nodal Line Semimetals

“…By replacing the standard Peierls and the ladder operator representation [ 40 , 49 ], the annihilation and creation operators are used, where , and , , . The Hamiltonian of type-II NLS is written as ( ): …”

“…By replacing the standard Peierls and the ladder operator representation [40,49], the annihilation a = l B…”

“…In the presence of a uniform magnetic field, the electron continuous energy spectrum will be transformed into discrete Landau levels, and the optical transition between the Landau energy levels will produce magneto-optical conductivity resonance peaks. In experiments, these resonance peaks can reflect the basic band structure [ 36 , 37 , 38 ], and the magneto-optical properties as a response function are also a particular experimental measure for topological materials [ 39 , 40 ]. Recent studies on magneto-optical properties have provided very useful information for topological semimetals [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ].…”