Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.469
Supercurrent in Graphene Josephson Junctions with Narrow Trenches in the Quantum Hall Regime Andrew Seredinski1,*, Anne Draelos1, Ming-Tso Wei1, Chung-Ting Ke1, Tate Fleming2, Yash Mehta2, Ethan Mancil2, Hengming Li2, Takashi Taniguchi3, Kenji Watanabe3, Seigo Tarucha4,5, Michihisa Yamamoto4,5, Ivan V. Borzenets6, François Amet2, and Gleb Finkelstein1 1
Department of Physics, Duke University, Durham, NC 27708, U.S.A.
2
Department of Physics and Astronomy, Appalachian State University, Boone, NC 28607, U.S.A.
3
Advanced Materials Laboratory, NIMS, Tsukuba 305-0044, Japan
4
Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 1-8656, Japan
5
Center for Emergent Matter Science (CEMS), RIKEN, Wako-shi, Saitama 351-0198, Japan
6
Department of Physics, City University of Hong Kong, Kowloon, Hong Kong SAR
* Corresponding author: Andrew Seredinski ([email protected])
ABSTRACT
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
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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.
INTRODUCTION Superconductor-quantum Hall heterostructures are predicted to host Majorana zero modes (MZMs) which could be harnessed for fault-tolerant quantum computing [1, 2, 3]. This has sparked a renewal of experimental interest in the intersection of quantum Hall physics and superconductivity [4, 5, 6, 7, 8, 9]. Recently, our group reported on supercurrent mediated by quantum Hall (QH) edge states in boron nitride (BN) encapsulated graphene [9, 10]. This follows theoretical predictions [11, 12] and raises the possibility of MZMs that could take advantage of the gate-tuneability of QH states. Exploration of higher applied magnetic fields and fractional quantum Hall states could yield parafermions: yet more exotic non-abelian anyons [13, 14]. The microscopic ori
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