Gate controlled valley polarizer in bilayer graphene

Hao Chen, Pinjia Zhou, Jiawei Liu, Jiabin Qiao, Barbaros Oezyilmaz and Jens Martin ()
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Hao Chen: National University of Singapore
Pinjia Zhou: National University of Singapore
Jiawei Liu: National University of Singapore
Jiabin Qiao: National University of Singapore
Barbaros Oezyilmaz: National University of Singapore
Jens Martin: National University of Singapore

Nature Communications, 2020, vol. 11, issue 1, 1-7

Abstract: 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.

Date: 2020
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DOI: 10.1038/s41467-020-15117-y

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