Charge transport in InAs nanowire Josephson junctions
Journal article, 2014

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.

Author

Simon Abay

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Daniel Persson

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

H. Nilsson

Lund University

F. Wu

Chalmers University of Technology

H. Q. Xu

Lund University

Peking University

Mikael Fogelström

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Vitaly Shumeiko

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

Per Delsing

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Physical Review B - Condensed Matter and Materials Physics

1098-0121 (ISSN)

Vol. 89 21 214508- 214508

Areas of Advance

Nanoscience and Nanotechnology

Roots

Basic sciences

Subject Categories

Condensed Matter Physics

DOI

10.1103/PhysRevB.89.214508