Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 2D-Dirac surface states and bulk gap probed via quantum capacitance in a
  3D topological insulator   BiSbTeSe$_2$ is a 3D topological insulator (3D-TI) with Dirac type surface
states and low bulk carrier density, as donors and acceptors compensate each
other. Dominating low temperature surface transport in this material is
heralded by Shubnikov-de Haas oscillations and the quantum Hall effect. Here,
we experimentally probe and model the electronic density of states (DOS) in
thin layers of BiSbTeSe$_2$ by capacitance experiments both without and in
quantizing magnetic fields. By probing the lowest Landau levels, we show that a
large fraction of the electrons filled via field effect into the system ends up
in (localized) bulk states and appears as a background DOS. The surprisingly
strong temperature dependence of such background DOS can be traced back to
Coulomb interactions. Our results point at the coexistence and intimate
coupling of Dirac surface states with a bulk many-body phase (a Coulomb glass)
in 3D-TIs.

12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th