Workshop book - Physikzentrum der RWTH Aachen - RWTH Aachen ...

Posters Tuesday February 5
Poster 30:
Topological edge states in a HgTe quantum well in proximity to an s-wave
superconductor
Luzie Weithofer
Topological insulators represent a new class of condensed matter systems
which are characterized by topologically protected edge states. Two-dimensional
topological insulators have been experimentally realized in HgTe
quantum wells [1]. In a HgTe quantum well in the topologically non-trivial
phase, two edge states of different spin propagate in opposite directions at
the same boundary.
Here, we consider the proximity-induced superconductivity in the bulk of
a HgTe quantum well in terms of a four-band model [2]. In addition, we
include various symmetry-breaking terms and discuss their consequences on
the topological properties of the system, focusing on the existence of edge
states.
[1] M. König et al., Science 318, 766 (2007) [2] B. Bernevig et al., Science
314, 1757 (2006)
Poster 31:
z→−z Symmetry of Spin-Orbit Coupling and Weak Localization in Graphene
Vladimir Falko
We show that the influence of spin-orbit (SO) coupling on the weak-localization
effect for electrons in graphene depends on the lack or presence of
z→−z symmetry in the system. While, for z→−z asymmetric SO coupling,
disordered graphene should display a weak antilocalization behavior at lowest
temperature, z→−z symmetric coupling leads to an effective saturation of
decoherence time which can be partially lifted by an in-plane magnetic field,
thus tending to restore the weak-localization effect.
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