Transport between superconductors coupled to quantum Hall edge modes

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Date/Time:Monday, 25 Oct 2010 from 4:10 pm to 5:10 pm
Location:Physics, Room 5
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James N. Eckstein (University of Illinois at Urbana-Champaign)

We are studying transport between Quantum Hall (QH) phases and superconducting electrodes. This requires a more transparent contact into the semiconductor than is usually obtained. Most semiconductors have a large surface Schottky barrier that dominates the contact conductance. To get good electronic coupling, we have developed an all in-situ multilayer growth architecture to form the contacts. These contacts provide a transmission probability per Landauer channel as high as 0.73. The electrons in the semiconductor near the surface of these samples show evidence, in special transport devices, of proximity induced pair correlations. We've also incorporated similar junctions, using high HC2 NbTi as the superconductor, onto the edges of QH devices. Transport between two adjacent superconducting electrodes occurs through the QH system. When the contacts are far apart, the junction conductance on QH plateaus is roughly proportional to the QH phase number, nu. For more closely spaced contacts an enhancement in the junction conductance is observed on a QH plateau. This is evidence for emerging coherence in these S-QH-S devices. Even narrower gap devices show a one sided (chiral) "supercurrent", the origin of which is currently being investigated.

*Work carried out by Stephanie Law-Toner and Michael Vissers