Dresden 2011 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 8: TR: Graphene 2 (jointly with MA, HL, and DY)
TT 8.6: Vortrag
Montag, 14. März 2011, 15:15–15:30, HSZ 304
Weak Localization versus Weak Antilocalization in Graphene — •Frank Ortmann1, Alessandro Cresti2, Gilles Montambaux3, and Stephan Roche4 — 1INAC/SPRAM, CEA Grenoble, France — 2IMEP-LAHC, Minatec, Grenoble, France — 3Laboratoire de Physique des Solides, Université Paris-Sud, Orsay, France — 4Institut Català de Nanotecnologia and CIN2, Universitat Autònoma de Barcelona, Barcelona, Spain
The understanding of quantum transport phenomena in graphene-based materials is the current subject of great excitation. In the presence of disorder, one of the predicted signatures of pseudospin is the change in sign of the quantum correction to the semiclassical Drude conductivity. This phenomenon, referred to as weak antilocalization (WAL), results from complex quantum-interferences of charge carriers in a disordered potential landscape and has been recently observed experimentally with weak-field magnetotransport measurements.
In this talk we present a numerical weak-field magnetotransport study of huge graphene samples and the influence of a realistic (long-range) disorder potential describing charges trapped in the gate oxide. Our simulations give clearly different magnetoconductance responses in different regimes which are fingerprint of either weak localization or WAL. Depending on the strength of the perturbing potential, the magnetoconductance can be tuned from positive to negative. The gate potential provides a second handle to modify these characteristics. Our results therefore shed new light on experiments and unveil the possible origin of crossovers from positive to negative magnetoconductance.