Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Landau level spectroscopy of massive Dirac fermions in
  single-crystalline ZrTe5 thin flakes   We report infrared magneto-spectroscopy studies on thin crystals of an
emerging Dirac material ZrTe5 near the intrinsic limit. The observed structure
of the Landau level transitions and zero-field infrared absorption indicate a
two-dimensional Dirac-like electronic structure, similar to that in graphene
but with a small relativistic mass corresponding to a 9.4 meV energy gap.
Measurements with circularly polarized light reveal a significant electron-hole
asymmetry, which leads to splitting of the Landau level transitions at high
magnetic fields. Our model, based on the Bernevig-Hughes-Zhang effective
Hamiltonian, quantitatively explains all observed transitions, determining the
values of the Fermi velocity, Dirac mass (or gap), electron-hole asymmetry, and
electron and hole g-factors.

2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg