Specular Electron Focusing between Gate-Defined Quantum Point Contacts in Bilayer Graphene

We report multiterminal measurements in a ballisticbilayer graphene(BLG) channel, where multiple spin- and valley-degenerate quantumpoint contacts (QPCs) are defined by electrostatic gating. By patterningQPCs 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 clearpeaks with comparable amplitudes and weak signatures of quantum interferenceat the lowest temperature, indicating that reflections at the gate-definededges are specular, and transport is phase coherent. The temperaturedependence of the focusing signal shows that, despite the small gate-inducedbandgaps in our sample (less than or similar to 45 meV), several peaks are visibleup to 100 K. The achievement of specular reflection, which is expectedto preserve the pseudospin information of the electron jets, is promisingfor the realization of ballistic interconnects for new valleytronicdevices.