Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metallization and proximity superconductivity in topological insulator
  nanowires   A heterostructure consisting of a topological insulator (TI) nanowire brought
into proximity with a superconducting layer provides a promising route to
achieve topological superconductivity and associated Majorana bound states
(MBSs). Here, we study effects caused by such a coupling between a thin layer
of an $s$-wave superconductor and a TI nanowire. We show that there is a
distinct phenomenology arising from the metallization of states in the TI
nanowire by the superconductor. In the strong coupling limit, required to
induce a large superconducting pairing potential, we find that metallization
results in a shift of the TI nanowire subbands ($\sim 20$ meV) as well as it
leads to a small reduction in the size of the subband gap opened by a magnetic
field applied parallel to the nanowire axis. Surprisingly, we find that
metallization effects in TI nanowires can also be beneficial. Most notably,
coupling to the superconductor induces a potential in the portion of the TI
nanowire close to the interface with the superconductor, this breaks inversion
symmetry and at finite momentum lifts the spin degeneracy of states within a
subband. As such coupling to a superconductor can create or enhance the subband
splitting that is key to achieving topological superconductivity. This is in
stark contrast to semiconductors, where it has been shown that metallization
effects always reduce the equivalent subband-splitting caused by spin-orbit
coupling. We also find that in certain geometries metallization effects can
reduce the critical magnetic required to enter the topological phase. We
conclude that, unlike in semiconductors, the metallization effects that occur
in TI nanowires can be relatively easily mitigated, for instance by modifying
the geometry of the attached superconductor or by compensation of the TI
material.

2
The categories of this paper are: math
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat