Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical investigation of thermoelectric topological crystalline
  insulator Pb$_{0.77}$Sn$_{0.23}$Se   Pb$_{0.77}$Sn$_{0.23}$Se is a novel alloy of two promising thermoelectric
materials PbSe and SnSe that exhibits a temperature dependent band inversion
below 300 K. Recent work has shown that this band inversion also coincides with
a trivial to nontrivial topological phase transition. To understand how the
properties critical to thermoelectric efficiency are affected by the band
inversion, we measured the broadband optical response of
Pb$_{0.77}$Sn$_{0.23}$Se as a function of temperature. We find clear optical
evidence of the band inversion at $160\pm15$ K, and use the extended Drude
model to accurately determine a $T^{3/2}$ dependence of the bulk carrier
lifetime, associated with electron-acoustic phonon scattering. Due to the high
bulk carrier doping level, no discriminating signatures of the topological
surface states are found, although their presence cannot be excluded from our
data.

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The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat