186 research outputs found
Stabilization of Majorana modes in vortices in the superconducting phase of topological insulators using topologically trivial bands
If superconductivity is induced in the metallic surface states of topological
insulators via proximity, Majorana modes will be trapped on the vortex cores.
The same effects hold for doped topological insulators which become bulk s-wave
superconductors as long as the doping does not exceed a critical values It is this critical chemical potential at which the material
forgets it arose from a band-inverted topological insulator; it loses its
topological \emph{imprint.} For the most common classes of topological
insulators, which can be modeled with a minimal 4-band Dirac model the values
of can be easily calculated, but for materials with more
complicated electronic structures such as HgTe or ScPtBi the result is unknown.
We show that due to the hybridization with an additional Kramers' pair of
topologically trivial bands the topological imprint of HgTe-like electronic
structures (which includes the ternary Heusler compounds) can be widely
extended for p-doping. As a practical consequence we consider the effects of
such hybridization on the range of doping over which Majorana modes will be
bound to vortices in superconducting topological insulators and show that the
range is strongly extended for p-doping, and reduced for n-doping. This leaves
open the possibility that other topological phenomena may be stabilized over a
wider range of doping.Comment: 5 pages, 1 figure, Accepted for publication in Physical Review
Letter
Majorana fermion exchange in strictly one dimensional structures
It is generally thought that adiabatic exchange of two identical particles is
impossible in one spatial dimension. Here we describe a simple protocol that
permits adiabatic exchange of two Majorana fermions in a one-dimensional
topological superconductor wire. The exchange relies on the concept of
"Majorana shuttle" whereby a domain wall in the superconducting order
parameter which hosts a pair of ancillary Majoranas delivers one zero mode
across the wire while the other one tunnels in the opposite direction. The
method requires some tuning of parameters and does not, therefore, enjoy the
full topological protection. The resulting exchange statistics, however,
remains non-Abelian for a wide range of parameters that characterize the
exchange.Comment: 5 pages, 4 figures, supplemental material is include
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