Andreev Reflection and Klein Tunneling in High-Temperature Superconductor-Graphene Junctions

Abstract

Scattering processes in quantum materials emerge as resonances in electronic transport, including confined modes, Andreev states, and Yu-Shiba-Rusinov states. However, in most instances, these resonances are driven by a single scattering mechanism. Here, we show the appearance of resonances due to the combination of two simultaneous scattering mechanisms, one from superconductivity and the other from graphene p-n junctions. These resonances stem from Andreev reflection and Klein tunneling that occur at two different interfaces of a hole-doped region of graphene formed at the boundary with superconducting graphene due to proximity effects from Bi 2 Sr 2 Ca 1 Cu 2 O 8þδ . The resonances persist with gating from p þ -p and p-n configurations. The suppression of the oscillation amplitude above the bias energy which is comparable to the induced superconducting gap indicates the contribution from Andreev reflection. Our experimental measurements are supported by quantum transport calculations in such interfaces, leading to analogous resonances. Our results put forward a hybrid scattering mechanism in graphene-high-temperature superconductor heterojunctions of potential impact for graphene-based Josephson junctions.

Andreev reflection in graphene nanoribbons induced by d-wave superconductors

“…The quantization of the wavevector imposed by the transverse confinement is responsible for the suppression. The transport properties in the junctions of graphene and a d-wave superconductor have been investigated not only theoretically [20][21][22][23][24] but also experimentally [25,26]. Here, the electronic states in the theoretical models were described using plane waves, i.e.…”