Published in Phys. Rev. X 4, 011201 (2014).
Friedel Oscillation-Induced Energy Gap Manifested as Transport Asymmetry at Monolayer-Bilayer Graphene Boundaries
Kendal W. Clark,1 X.-G. Zhang,1 Gong Gu,2 Jewook Park,1 Guowei He,3 Randall M. Feenstra,3 and An-Ping Li1
1Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
2Department of Electrical Engineering & Computer Science, University of Tennessee, Knoxville, TN 37996, USA
3Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
Abstract
We show that Friedel charge oscillation near an interface opens a gap at the Fermi energy for electrons with wave vectors perpendicular to the interface. If the Friedel gaps on two sides of the interface are different, a nonequlibrium effect – shifting of these gaps under bias – leads to asymmetric transport upon reversing the bias polarity. The predicted transport asymmetry is revealed by scanning tunneling potentiometry at monolayer-bilayer interfaces in epitaxial graphene on SiC (0001). This intriguing interfacial transport behavior opens a new avenue towards novel quantum functions such as quantum switching.
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