Probing quantum phase slips in superconducting nanowires modified using high bias voltage pulses

Quantum phase slips (QPS) or the macroscopic quantum tunneling (MQT) of a nanowire’s order parameter through an activation energy barrier have remained the subject of intense debate for many years. They are expected to occur at low enough temperature where thermally activated phase slips (TAPS) have been frozen out in analogy with Josephson junctions where the macroscopic tunneling of phase at low temperatures has been conclusively experimentally demonstrated. We address this question by following a similar experimental strategy to that employed for establishing MQT in JJs. By measuring switching current distributions, we can probe the phase slip rate and determine if it corresponds to thermal activation or quantum tunneling. Having established that the behavior we see is consistent with being in the quantum regime, we can alter properties of the nanowires and see if the response is consistent with the expectations of the quantum model. To do this we employ an in-situ modification technique using high bias voltage pulses. Using these pulses, we can change resistance, critical temperature, critical current and morphology of the nanowire. We can also change the shunting capacitance of the nanowire by altering the photolithography step used to create the nanowires electrodes. The resulting response of the nanowires agrees well with being in the quantum tunneling dominated regime. An interesting side benefit of the pulsing technique is that we can exactly set the nanowires switching current to a desired value. This may be instrumental in the development of superconducting nanowire qubits.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Aref, Thomas

Contributors dc:contributor

• Bezryadin, Alexey
• Eckstein, James N.
• Oono, Yoshitsugu
• Ha, Taekjip

• quantum phase slip
• superconducting nanowires
• electromigration
• pulsing
• high bias voltage
• QPS
• TAPS
• phase slip

Statement dc:rights

• Copyright 2010 by Thomas Aref. All rights reserved.

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/18460

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/18460