Measurements of weak localization of graphene in inhomogeneous magnetic fields
N. Lindvall+, A. Shivayogimath*, A. Yurgens+
+Chalmers University of Technology/MC2, SE-41296 Gothenburg, Sweden
*DTU Nanotech - Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
Abstract
Weak localization in graphene is studied in inhomogeneous magnetic
fields. To generate the inhomogeneous field, a thin film of type-II
superconducting niobium is put in close proximity to graphene. A deviation from
the ordinary quadratic weak localization behavior is observed at low fields. We
attribute this to the inhomogeneous field caused by vortices in the
superconductor. The deviation, which depends on the carrier concentration in
graphene, can be tuned by the gate voltage. In addition, collective vortex
motion, known as vortex avalanches, is observed through magnetoresistance
measurements of graphene.