Physics Seminar (This Seminar is Cancelled)
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  • Physics Seminar (This Seminar is Cancelled)

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Title: New phenomena in transport through suspended graphene devices

Speaker: Alberto Morpurgo (University of Geneva)

Date/Time: April 13, 2015 Monday at 13:40

Place: Sabancı University, FENS L062

Some of the most interesting electronic properties of graphene –and of
its multilayers– occur when the Fermi level is positioned very close
to the charge neutrality point, where valence and conduction bands
touch. For devices where graphene is in direct contact with a
substrate, the possibility to position the Fermi level close to the
charge neutrality point is limited by the presence of charge
inhomogeneity, which so far has not be reduced below ~5 1010 cm-2 even
in the best systems. In suspended graphene devices –where graphene is
not in direct contact with a gate dielectric material– this limit can
be improved by nearly a factor of 50, enabling the observation of new
phenomena. Here, I will discuss transport experiments that we have
performed on devices of this high quality, by probing transport in a
multi-terminal configuration –something that had not been successfully
done until now. After giving some background about suspended graphene
devices and presenting the characterization of our structures, I will
discuss two main topics. The first is the fractional quantum Hall
effect in graphene bilayers, where the phenomenon occurs in new
regimes, resulting in predicted exotic states, whose manifestations
seems to be present in our data. The second is the opening of a gap at
charge neutrality induced by electron-electron interactions that is
known to occur in bilayers, and that we now observe also in four-layer
graphene. Our experimental results suggest the presence of an even-odd
effect of interactions with layer thickness that persists even in
multilayers that are so thick to be normally considered to be
graphite, as long as no structural defects are present.

contact: İsmet İnönü Kaya