Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 28: Moire and Graphene Stacking
O 28.7: Vortrag
Dienstag, 17. März 2015, 15:30–15:45, MA 041
Reversible sublattice symmetry breaking in monolayer graphene nanomembranes using tip induced pseudomagnetic fields — •Alexander Georgi1, Peter Nemes-Incze1, Ramon Carillo-Bastos2, Daiara Faria2, Marco Pratzer1, Ludger Wirtz3, Nancy Sandler2, and Markus Morgenstern1 — 12.Physikalisches Institut B RWTH Aachen University — 2Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University — 3Physics and Materials Science Research Unit, University of Luxembourg
Strain engineering in graphene might lead to a new generation of electromechanical devices, in particular due to its tunable pseudomagnetic field being a property of the unique sublattice degree of freedom within the honeycomb lattice. However, possibilities to tune the pseudomagnetic field on the nanoscale have not been realized so far. Here, we show that the forces of the tip of a scanning tunneling microscope can be used to switch local fields on and off, by applying strain, as visible by a relative change of the local density of states of the two sublattices up to 30 %. Comparison with tight binding simulations reveals that this contrast corresponds to a local pseudomagnetic field of up to 500 T.
We carefully rule out other possibilities for the apparent sublattice symmetry breaking such as buckling, a local Peierls transition, different lifting forces of the tip above different sublattices, or the correlation of electric and pseudomagnetic fields. Moreover, we show that model calculations of the van-der Waals forces between tip and graphene reproduce the observed effects quantitatively within 50 %.