Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 64: Poster Session: Transport
TT 64.3: Poster
Donnerstag, 4. April 2019, 15:00–18:30, Poster D
Superconducting proximity effect and conductance quantization in bilayer graphene quantum wires — •Vanessa Gall1,2 and Igor Gornyi1,2 — 1Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe, Germany — 2Institute for Condensed Matter Theory, Karlsruhe Institute of Technology, Karlsruhe, Germany
Quantum wires or Quantum Point Contacts (QPCs) built from two dimensional material, like bilayer graphene (BLG), might pave the way towards quantum circuits. We consider a gate defined BLG based quantum wire with a perpendicular magnetic field and both superconducting and non superconducting leads. In the superconducting regime we study the magnetic interference pattern in rectangular junctions by means of a semi-classical model. A similar study was recently conducted on BLG QPCs, where it could be shown, that a variation in the gate potentials leads to a tailoring of the supercurrent. Here we find a dependence on the aspect ratio, where scattering off the side edges is of high importance in narrow junctions, but not in wide ones. In the normal conducting regime, we investigate the quantized conductance due to finite size effects and the emergence of Landau levels. We find an accidential degeneracy for wide channels and large gaps. The experimental confirmation in the case of BLG QPCs was recently given. The conduction plateaus of height 4e2/h are clearly visible and the first step has a height of 8e2/h for certain values of the splitgate. The conditions for this accidential degeneracy can be expressed analytically by means of the effective two band hamiltonian.