Regensburg 2016 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 86: Graphene: Electronic Properties and Structure
(Joint session of DS, DY, HL, MA, O and TT organized by O)
TT 86.3: Talk
Friday, March 11, 2016, 11:00–11:15, S051
Direct measurement of chiral symmetry breaking in strained graphene by STM — Alexander Georgi1, •Peter Nemes-Incze1, Ramon Carillo-Bastos2, Martin Schneider3, Dinesh Subramaninam1, Torge Mashoff4, Daiara Faria2,5, Silvia Viola Kusminskiy3, Dawei Zhai2, Marcus Liebmann1, Marco Pratzer1, Ludger Wirtz6, Nancy Sandler2, and Markus Morgenstern1 — 1RWTH Aachen Univ. and JARA-FIT, Aachen, Germany — 2Ohio Univ., Athens, Ohio, USA — 3Freie Univ. Berlin, Berlin, Germany — 4Johannes Gutenberg-Univ., Mainz, Germany — 5Univ. Federal Fluminense, Niterói, Brazil — 6Univ. of Luxembourg, Luxembourg
The breaking of reflection symmetry has important consequences for pseudospin 1/2 particles, such as those used to describe low-energy excitations in graphene. Here we show that forces exerted by the tip of a scanning tunneling microscope induce mechanical strain on sub-nm length scales that acts as a gauge field breaking the chiral symmetry of the system. The parity violation manifests itself as a redistribution of the local density of states between the two sublattices by up to 30%. The effect can be understood as a pseudospin polarization due to a pseudo-Zeeman shift produced by the strain induced pseudo-magnetic field. This interpretation is supported by tight binding simulations and effective Dirac model calculations. The tunable pseudo-magnetic field might be used for the ultra fast separation of electrons of different valleys providing a switchable valley filter as a basic element for valleytronics.