Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 10: Focus Session: Superconductivity in 2d-Materials and their Heterostructures
TT 10.5: Invited Talk
Tuesday, September 6, 2022, 11:45–12:15, H3
Minigap and Andreev bound states in ballistic graphene — •Luca Banszerus1,2, Florian Libisch3, Andrea Ceruti1, Stefan Blien4, Kenji Watanabe5, Takashi Taniguchi5, Andreas Hüttel4, Bernd Beschoten1, Fabian Hassler1, and Christoph Stampfer1 — 1RWTH Aachen University, Germany — 2Forschungszentrum Jülich, Germany — 3TU Vienna, Austria — 4University of Regensburg, Germany — 5National Institute for Materials Science, Japan
A finite-size normal conductor, proximity-coupled to a superconductor has been predicted to exhibit a so-called minigap, in which quasiparticle excitations are prohibited. In this talk, we demonstrate the direct observation of such a minigap through transport measurements on partially gated ballistic graphene, coupled to superconducting MoRe contacts [1]. The minigap is probed by finite bias spectroscopy through a weakly coupled junction in the graphene region and its value is given by the dimensions of the device. Besides the minigap, a distinct peak in the differential resistance is observed, which we attribute to weakly coupled Andreev bound states (ABS) located near the superconductor-graphene interface. For weak magnetic fields, the phase accumulated in the normal-conducting region shifts the ABS in quantitative agreement with predictions from tight-binding calculations based on the Bogolioubov-de Gennes equation as well as with an analytical semiclassical model.
[1] arXiv:2011.11471