Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electrons on the surface of Bi2Se3 form a topologically-ordered two
  dimensional gas with a non-trivial Berry's phase   The interface between a superconductor and a topological insulator has been
proposed to harbor novel quasiparticles that realize physical schemes for
fault-tolerant quantum computation. Here, we present high resolution
angle-resolved photoemission experimental results, which along with first
principles calculations, suggest that the surface-edge states of Bi2Se3 form a
topological 2D metal. When magnetic atoms are deposited, the surface tends to
lose Kramers' degeneracy and a k-space connection thread between the bulk
valence and conduction bands is lost. Our observed states carry a \pi Berry's
phase suggesting that although the real materials are often electron doped
fully undoped Bi2Se3 would be a Z2 topological insulator at room temperature.

7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin