Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of Anderson localization in ultrathin films of
  three-dimensional topological insulators   Anderson localization, the absence of diffusive transport in disordered
systems, has been manifested as hopping transport in numerous electronic
systems, whereas in recently discovered topological insulators it has not been
directly observed. Here we report experimental demonstration of transition from
diffusive transport in the weak antilocalization regime to variable range
hopping transport in the Anderson localization regime with ultrathin
(Bi$_{1-x}$Sb$_x$)$_2$Te$_3$ films. As disorder becomes stronger, negative
magnetoconductivity due to the weak antilocalization is gradually suppressed,
and eventually positive magnetoconductivity emerges when the electron system
becomes strongly localized. This works reveals the critical role of disorder in
the quantum transport properties of ultrathin topological insulator films, in
which theories have predicted rich physics related to topological phase
transitions.

19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con