Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 5: Graphene - Magnetic Fields (jointly with DS, HL, MA, O)

TT 5.1: Talk

Monday, March 11, 2013, 09:30–09:45, H17

Quantum interference in an electron-hole graphene ring system — •Dmitri Smirnov, Hennrik Schmidt, and Rolf J. Haug — Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2 30167 Hannover, Germany

We analyze the electronic properties of a topgated monolayer graphene ring. Micro-mechanical cleavage was used to place a flake on a Si/SiO2 substrate. The structuring and contacting was done via plasma etching and electron beam lithography. An additional gate was placed on top of one arm of the ring which allows us to control the charge carrier concentration locally and additionally to create a pnp- (npn-) junction inside the ring. The sample was measured in a He3 cryostat and is identified as single layer graphene via magnetotransport measurements.
We observe Aharonov Bohm (AB) effect by sweeping the magnetic field around 0 T. The period of the oscillations is approx. 16 mT which fits the size of the ring well. The AB-oscillations are measured for different temperatures and the amplitude shows a saturation for lower temperatures. We also observe the AB-oscillations when a pnp-junction is created inside the ring. The period is independent of the existence of a pnp-junction and stays constant in all situations. We analyze the amplitude in dependence of the charge carrier concentration. The absolute amplitude is constant in the bipolar and unipolar region [1].

[1] D.Smirnov. et. al, Appl. Phys. Lett. 100, 203114 (2012).