Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thickness driven topological quantum phase transition and experimental
  evidence of Dirac semimetal state in Cr-doped Bi2Se3   In this report, we demonstrate that the energy gap in Cr-doped Bi2Se3 closes
and reopens in oscillatory fashion with increasing sample thickness indicating
the topological quantum phase transition driven by the quantum finite size
effect. The pattern of the oscillation provides an evidence that Cr-doped
Bi2Se3 can have a Dirac semimetal state depending on the sample thickness and
Cr-content. This resolves the puzzle of non-magnetic gap opening at the Dirac
point of topological insulators. An energy gap can be opened due to the quantum
finite size confinement of the bands in Dirac semimetal state. In addition, our
room temperature ARPES measurements revealed a topological quantum phase
transition between x = 0.06 and x = 0.08 in 7 quintuple layers Bi2-xCrxSe3
without ferromagnetism.

23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con