Specular Electron Focusing between Gate-Defined Quantum Point Contacts in Bilayer Graphene
J. Ingla Aynés (TU Delft - QN/van der Zant Lab, Kavli institute of nanoscience Delft)
Antonio L.R. Rigotti Manesco (TU Delft - QN/Akhmerov Group, Kavli institute of nanoscience Delft)
Talieh S. Ghiasi (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
Serhii Volosheniuk (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
Kenji Watanabe (National Institute for Materials Science)
Takashi Taniguchi (National Institute for Materials Science)
H. S J van der Zant (Kavli institute of nanoscience Delft, TU Delft - QN/van der Zant Lab)
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Abstract
We report multiterminal measurements in a ballistic bilayer graphene (BLG) channel, where multiple spin- and valley-degenerate quantum point contacts (QPCs) are defined by electrostatic gating. By patterning QPCs of different shapes along different crystallographic directions, we study the effect of size quantization and trigonal warping on transverse electron focusing (TEF). Our TEF spectra show eight clear peaks with comparable amplitudes and weak signatures of quantum interference at the lowest temperature, indicating that reflections at the gate-defined edges are specular, and transport is phase coherent. The temperature dependence of the focusing signal shows that, despite the small gate-induced bandgaps in our sample (≲45 meV), several peaks are visible up to 100 K. The achievement of specular reflection, which is expected to preserve the pseudospin information of the electron jets, is promising for the realization of ballistic interconnects for new valleytronic devices.
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