title: Tuning the Pseudospin Polarization of Graphene by a Pseudomagnetic Field.
abstract: One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudomagnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting from this pseudomagnetic field has been measured using scanning tunneling microscopy. Here we show that a signature of the pseudomagnetic field is a local sublattice symmetry breaking observable as a redistribution of the local density of states. This can be interpreted as a polarization of graphene's pseudospin due to a strain induced pseudomagnetic field, in analogy to the alignment of a real spin in a magnetic field. We reveal this sublattice symmetry breaking by tunably straining graphene using the tip of a scanning tunneling microscope. The tip locally lifts the graphene membrane from a SiO2support, as visible by an increased slope of the I(z) curves. The amount of lifting is consistent with molecular dynamics calculations, which reveal a deformed graphene area under the tip in the shape of a Gaussian. The pseudomagnetic field induced by the deformation becomes visible as a sublattice symmetry breaking which scales with the lifting height of the strained deformation and therefore with the pseudomagnetic field strength. Its magnitude is quantitatively reproduced by analytic and tight-binding models, revealing fields of 1000 T. These results might be the starting point for an effective THz valley filter, as a basic element of valleytronics.
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Georgi
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Peter
authors.identifier: 0000-0002-1222-3020
authors.initials: P
authors.lastname: Nemes-Incze
authors.affiliation: Facultad de Ciencias, Universidad Autónoma de Baja California , 21100 Mexicali, Baja California México.|Department of Physics and Astronomy, Ohio University , Athens, Ohio 45701, United States.
authors.forename: Ramon
authors.initials: R
authors.lastname: Carrillo-Bastos
authors.affiliation: Instituto Politécnico, Universidade do Estado de Rio de Janeiro , 28625-570 Nova Friburgo, Brasil.|Instituto de Física, Universidade Federal Fluminense , Niterói, 24210-340 Rio de Janeiro Brazil.
authors.forename: Daiara
authors.initials: D
authors.lastname: Faria
authors.affiliation: Dahlem Center for Complex Quantum Systems and Institut für Theoretische, Freie Universität Berlin , 14195 Berlin, Germany.|Institute for Theoretical Physics II, University of Erlangen-Nüremberg , 91058 Erlangen, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Viola Kusminskiy
authors.affiliation: Department of Physics and Astronomy, Ohio University , Athens, Ohio 45701, United States.
authors.forename: Dawei
authors.initials: D
authors.lastname: Zhai
authors.affiliation: Dahlem Center for Complex Quantum Systems and Institut für Theoretische, Freie Universität Berlin , 14195 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Schneider
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Dinesh
authors.initials: D
authors.lastname: Subramaniam
authors.affiliation: Johannes Gutenberg-Universität , 55122 Mainz, Germany.
authors.forename: Torge
authors.initials: T
authors.lastname: Mashoff
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Nils M
authors.identifier: 0000-0002-5043-6385
authors.initials: NM
authors.lastname: Freitag
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Liebmann
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Pratzer
authors.affiliation: Physics and Materials Science Research Unit, University of Luxembourg , L-1511 Luxembourg, Luxembourg.
authors.forename: Ludger
authors.initials: L
authors.lastname: Wirtz
authors.affiliation: School of Physics and Astronomy, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Woods
authors.affiliation: School of Physics and Astronomy, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Roman V
authors.initials: RV
authors.lastname: Gorbachev
authors.affiliation: School of Physics and Astronomy, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Yang
authors.initials: Y
authors.lastname: Cao
authors.affiliation: School of Physics and Astronomy, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Kostya S
authors.initials: KS
authors.lastname: Novoselov
authors.affiliation: Department of Physics and Astronomy, Ohio University , Athens, Ohio 45701, United States.
authors.forename: Nancy
authors.initials: N
authors.lastname: Sandler
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , 52062 Aachen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Morgenstern
keywords: Graphene; STM; pseudomagnetic field; pseudospin polarization; strain; valley filter