Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Disorder Effects in the Bipolaron System Ti$_{4}$O$_{7}$ Studied by
  Photoemission Spectroscopy   We have performed a photoemission study of Ti$_{4}$O$_{7}$ around its two
transition temperatures so as to cover the metallic, high-temperature
insulating (bipolaron-liquid), and low-temperature insulating
(bipolaron-crystal) phases. While the spectra of the low-temperature insulating
phase show a finite gap at the Fermi level, the spectra of the high-temperature
insulating phase are gapless, which is interpreted as a soft Coulomb gap due to
dynamical disorder. We suggest that the spectra of the high-temperature
disordered phase of Fe$_{3}$O$_{4}$, which exhibits a charge order-disorder
transition (Verwey transition), can be interpreted in terms of a Coulomb gap.

29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an