Browsing by Author "Mehta, Y"

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    Chiral quasiparticle tunneling between quantum Hall edges in proximity with a superconductor
    (Physical Review B, 2019-09-10) Wei, MT; Draelos, AW; Seredinski, A; Ke, CT; Li, H; Mehta, Y; Watanabe, K; Taniguchi, T; Yamamoto, M; Tarucha, S; Finkelstein, G; Amet, F; Borzenets, IV
    © 2019 American Physical Society. We study a two-terminal graphene Josephson junction with contacts shaped to form a narrow constriction, less than 100nm in length. The contacts are made from type-II superconducting contacts and able to withstand magnetic fields high enough to reach the quantum Hall regime in graphene. In this regime, the device conductance is determined by edge states, plus the contribution from the constricted region. In particular, the constriction area can support supercurrents up to fields of ∼2.5T. Additionally, enhanced conductance is observed through a wide range of magnetic fields and gate voltages. This additional conductance and the appearance of supercurrent is attributed to the tunneling between counterpropagating quantum Hall edge states along opposite superconducting contacts.
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    Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime
    (MRS Advances, 2018-01-01) Seredinski, A; Draelos, A; Wei, MT; Ke, CT; Fleming, T; Mehta, Y; Mancil, E; Li, H; Taniguchi, T; Watanabe, K; Tarucha, S; Yamamoto, M; Borzenets, IV; Amet, F; Finkelstein, G
    © 2018 Materials Research Society. Coupling superconductors to quantum Hall edge states is the subject of intense investigation as part of the ongoing search for non-abelian excitations. Our group has previously observed supercurrents of hundreds of picoamperes in graphene Josephson junctions in the quantum Hall regime. One of the explanations of this phenomenon involves the coupling of an electron edge state on one side of the junction to a hole edge state on the opposite side. In our previous samples, these states are separated by several microns. Here, a narrow trench perpendicular to the contacts creates counterpropagating quantum Hall edge channels tens of nanometres from each other. Transport measurements demonstrate a change in the low-field Fraunhofer interference pattern for trench devices and show a supercurrent in both trench and reference junctions in the quantum Hall regime. The trench junctions show no enhancement of quantum Hall supercurrent and an unexpected supercurrent periodicity with applied field, suggesting the need for further optimization of device parameters.