The current-phase relation of graphene-based Josephson junctions

The current-phase relation (CPR) of a Josephson junction reveals valuable information about the microscopic processes and symmetries that influence the supercurrent. For the work described in this thesis, we have studied the CPR of graphene-based Jospehson junctions, inspired by previous theoretical predictions of a departure from the usual sinusoidal functionality, or skewness, of the CPR. The experimental data was obtained by incorporating the junction into an rf SQUID geometry coupled to a dc SQUID magnetometer, a technique usually referred to as phase-sensitive SQUID interferometry, which allows for the direct measurement of the phase difference across the junction. While some of the predictions from theory - like the departure of the CPR from sinusoidal behavior, its symmetry with carrier nature and the de-skewing with increasing temperature - were qualitatively observed, others were inconsistent with the experimental data. Perhaps the most important disparity was that of the functionality of the skewing, which we found to vary linearly with critical current (Ic ), independent of the carrier density/temperature combination used to attain Ic. It is worth mentioning that our measurements have prompted renewed theoretical interest in this system, culminating in the modification of the original model to include the effects of temperature, and a recent publication venturing an explanation for the observed linearity of the CPR skewness with Ic.

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

• Chialvo, Cesar E.

Contributors dc:contributor

• Mason, Nadya
• Eckstein, James N.
• Stone, Michael
• Gollin, George D.

• Graphene
• current-phase relation (CPR)
• Josephson junctions
• nano-fabrication
• micro-fabrication

Statement dc:rights

• Copyright 2011 Cesar E. Chialvo

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/24247

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/24247