Kavli Affiliate: Herre S. J. Van Der Zant
| First 5 Authors: Josep Ingla-Aynés, Antonio L. R. Manesco, Talieh S. Ghiasi, Kenji Watanabe, Takashi Taniguchi
| Summary:
The achievement of valley-polarized electron currents is a cornerstone for
the realization of valleytronic devices. Here, we report on ballistic coherent
transport experiments where two opposite quantum point contacts (QPCs) are
defined by electrostatic gating in a bilayer graphene (BLG) channel. By
steering the ballistic currents with an out-of-plane magnetic field we observe
two current jets, a consequence of valley-dependent trigonal warping. Tuning
the BLG carrier density and number of QPC modes (m) with a gate voltage we find
that the two jets are present for m=1 and up to m=6, indicating the robustness
of the effect. Semiclassical simulations which account for size quantization
and trigonal warping of the Fermi surface quantitatively reproduce our data
without fitting parameters, confirming the origin of the signals. In addition,
our model shows that the ballistic currents collected for non-zero magnetic
fields are valley-polarized independently of m, but their polarization depends
on the magnetic field sign, envisioning such devices as ballistic current
sources with tuneable valley-polarization.
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