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

Talks Wednesday February 6
Interference and interaction in ultraclean suspended monolayer and bilayer
graphene
Christian Schönenberger, University of Basel, Switzerland
We first show that graphene (monolayer and bilayer) with exceptional high
mobilities approaching 100 m 2 /Vs can be obtained when suspended and insitu
current annealed. Using such materials, we then first summarize recent
results obtained with bilayer graphene where a pronounced gap emerges at
the charge-neutrality point. This gap forms in zero electric and magnetic field
and is thought to be accompanied by a transition into a broken symmetry
state. The precise nature of this ground state is currently debated. We show
that our results are consistent with both the layer anti-ferromagnetic state
(LAF) and the quantum-spin Hall state (QSH). While we cannot distinguish
these two states, we can exclude the quantum anomalous Halls state based
on electrical measurements in parallel magnetic field.
We further will demonstrate electrical transport experiments in monolayer
graphene with top gates arranged in the form of strips. The gates allow to
define n-p regions yielding a peculiar interference pattern in high mobility
samples caused by Klein tunneling.
Coauthors:
Frank Freitag, Peter Rickhaus, Romain Maurand, Jelena Trbovic, Markus
Weiss and Christian Schönenberger
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