Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin Response of Electrons on the Surface of a Topological Insulator   The surface of a topological insulator hosts a very special form of a
quasi-two dimensional metallic system when it is embedded in a topologically
trivial medium like the vacuum. The electronic properties of this unusual 2D
metal are distinct in many aspects from both the conventional two-dimensional
electron gas systems in quantum well heterostructures as well as those of a
single layer graphene. In this paper, we study one of these distinct features
i.e., the response of the electronic spins to an applied magnetic field
perpendicular to the surface. We find an unusual behaviour of the spin
magnetization and susceptibility as a function of both the magnetic field and
the chemical potential for a generic topological surface. We propose that this
behavior could be studied by the recently developed experimental technique
called \beta NMR which is highly sensitive to the surface electron spins. We
explain how this technique could be used to probe for spontaneous magnetic
ordering caused by magnetic dopants or interactions discussed in the recent
literature.

2
The categories of this paper are: math
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph