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

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Degree programme
Physical Review Letters, Volume 130, issue 15
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 Bi2Sr2Ca1Cu2O8+δ. The resonances persist with gating from p+−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.
This work was supported by funding from the U.S. Naval Research Laboratory Grant No. N00173-19-1-G0008. J. L. L. acknowledges the computational resources provided by the Aalto Science-IT project and the financial support from the Academy of Finland Projects No. 331342 and No. 336243. The work at Brookhaven National Laboratory was supported by the U.S. Department of Energy (DOE) the Office of Basic Energy Sciences, Materials Sciences, and Engineering Division under Contract No. DESC0012704.
Other note
Jois , S , Lado , J , Gu , G , Li , Q & Lee , J U 2023 , ' Andreev Reflection and Klein Tunneling in High-Temperature Superconductor-Graphene Junctions ' , Physical Review Letters , vol. 130 , no. 15 , 156201 , pp. 1-6 .