Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Enhanced thermoelectric performance in thin films of three-dimensional
  topological insulators   Thermoelectric (TE) devices have been attracting increasing attention because
of their ability to convert heat directly to electricity. To date, improving
the TE figure of merit remains the key challenge. The advent of the topological
insulator and the emerging nanotechnology open a new way to design
high-performance TE devices. In this paper, we investigate the TE transport
properties of the Bi2Se3 thin film by the first-principle calculations and the
Boltzmann transport theory. By comparing our calculations with the earlier
experimental data, we demonstrate that, for the Bi2Se3 film of thickness larger
than six quintuple layers, the relaxation time of the topological surface
states in the bulk gap is about hundreds of femtoseconds, which is about two
orders larger than that of the bulk states. Such a large relaxation-time
difference causes the ratio of the electrical conductance to the thermal
conductance much larger than the value predicted by the Wiedemann-Franz law, as
well as the large magnitude of Seebeck coefficient, and consequently the large
TE figure of merit, when the Fermi level is near the conduction band edge. We
shows that the TE performance can be further improved by introducing defects in
the middle layers of the thin film. The improvement is generally significant at
room temperature and can be further enhanced at higher temperature.

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The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph