Charge transport in InAs nanowire Josephson junctions

Simon Abay, Daniel Persson, Henrik Nilsson, Fan Wu, H. Q. Xu, Mikael Fogelström, Vitaly Shumeiko, and Per Delsing
Phys. Rev. B 89, 214508 – Published 23 June 2014

Abstract

We present an extensive experimental and theoretical study of the proximity effect in InAs nanowires connected to superconducting electrodes. We fabricate and investigate devices with suspended gate-controlled nanowires and nonsuspended nanowires, with a broad range of lengths and normal-state resistances. We analyze the main features of the current-voltage characteristics: the Josephson current, excess current, and subgap current as functions of length, temperature, magnetic field, and gate voltage, and compare them with theory. The Josephson critical current for a short-length device, L=30 nm, exhibits a record high magnitude of 800 nA at low temperature that comes close to the theoretically expected value. The critical current in all other devices is typically reduced compared to the theoretical values. The excess current is consistent with the normal resistance data and agrees well with the theory. The subgap current shows a large number of structures; some of them are identified as subharmonic gap structures generated by multiple Andreev reflection. The other structures, detected in both suspended and nonsuspended devices, have the form of voltage steps at voltages that are independent of either the superconducting gap or length of the wire. By varying the gate voltage in suspended devices, we are able to observe a crossover from typical tunneling transport at large negative gate voltage, with suppressed subgap current and negative excess current, to pronounced proximity junction behavior at large positive gate voltage, with enhanced Josephson current and subgap conductance as well as a large positive excess current.

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  • Received 8 November 2013
  • Revised 16 May 2014

DOI:https://doi.org/10.1103/PhysRevB.89.214508

©2014 American Physical Society

Authors & Affiliations

Simon Abay1,*, Daniel Persson1, Henrik Nilsson2, Fan Wu1, H. Q. Xu2,3, Mikael Fogelström1, Vitaly Shumeiko1, and Per Delsing1,†

  • 1Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, SE-412 96 Göteborg, Sweden
  • 2Division of Solid State Physics, Lund University, Box 118, S-221 00 Lund, Sweden
  • 3Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China

  • *abay@chalmers.se
  • per.delsing@chalmers.se

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Issue

Vol. 89, Iss. 21 — 1 June 2014

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