Gate controlled valley polarizer in bilayer graphene.

Nature Communications
Hao ChenJens Martin

Abstract

Sign reversal of Berry curvature across two oppositely gated regions in bilayer graphene can give rise to counter-propagating 1D channels with opposite valley indices. Considering spin and sub-lattice degeneracy, there are four quantized conduction channels in each direction. Previous experimental work on gate-controlled valley polarizer achieved good contrast only in the presence of an external magnetic field. Yet, with increasing magnetic field the ungated regions of bilayer graphene will transit into the quantum Hall regime, limiting the applications of valley-polarized electrons. Here we present improved performance of a gate-controlled valley polarizer through optimized device geometry and stacking method. Electrical measurements show up to two orders of magnitude difference in conductance between the valley-polarized state and gapped states. The valley-polarized state displays conductance of nearly 4e2/h and produces contrast in a subsequent valley analyzer configuration. These results pave the way to further experiments on valley-polarized electrons in zero magnetic field.

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Citations

Mar 6, 2021·Journal of Chemical Information and Modeling·Anastasios Gotzias
Apr 24, 2021·Physical Review Letters·P PandeyD Beckmann
Jun 24, 2021·Nanotechnology·Zibo WangHua Jiang

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Methods Mentioned

BETA
electron beam lithography
scanning electron microscopy
atomic force microscopy

Software Mentioned

MATLAB

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