Supercurrent in the quantum Hall regime

Date: 
10/23/2018 - 4:00pm to 5:00pm
Location: 
CP 179
Speaker(s) / Presenter(s): 
Gleb Finkelstein, Duke University
Type of Event (for grouping events):
One of the promising routes towards creating novel topological states and excitations is to combine superconductivity with quantum Hall (QH) effect. However, signatures of superconductivity in the QH regime remain scarce, and a superconducting current through a QH weak link has so far eluded experimental observation. Here, we explore high mobility graphene/boron nitride heterostructures contacted by type II superconducting electrodes that could withstand  magnetic fields of a few Tesla. At low magnetic fields, our devices demonstrate the Fraunhoffer pattern and Fabri-Perot oscillations, confirming their uniformity and ballisticity. At fields of 1-2 Tesla, when Landau quantization is fully developed, regions of superconductivity can be observed on top of the conventional QH fan diagram. The measured supercurrent is very small, on a few nA scale, and periodic in magnetic field. I discuss possible mechanisms that could mediate supercurrent along the QH edge states.
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