Dresden 2011 – scientific programme
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MA: Fachverband Magnetismus
MA 56: Graphene (jointly with DY, DS, HL, O, TT)
MA 56.4: Talk
Thursday, March 17, 2011, 16:00–16:15, HSZ 401
The graphene Landau quartet unveiled — •Sander Otte1,2,3, Young Jae Song2,3, and Joseph Stroscio2 — 1Delft University of Technology, The Netherlands — 2National Institute of Standards and Technology (NIST), USA — 3Maryland NanoCenter, University of Maryland, USA
Some of the unique properties of graphene come to expression when its electrons are locked into Landau levels in an external magnetic field. Due to spin-degeneracy in combination with the two-atom unit cell of the hexagonal lattice (valley degeneracy), each Landau level is expected to host four electrons. We use a newly completed dilution refrigerator cooled STM system to study epitaxial graphene at 10 mK in magnetic fields up to 15 T. The unparalleled energy resolution of this instrument enables us to break the predicted fourfold Landau level degeneracy and to measure the sublevel splittings as a function of the magnetic field. Surprisingly large splittings are found for the valley states, which are not magnetic by nature. In addition, intriguing partial filling of the sublevels is observed, yielding access to promising electron correlation effects.