Microwave Spectroscopy and Transport Measurements of Andreev Bound States in Superconductor – Semiconductor Josephson Junctions

The physics of superconductor-semiconductor hybrid junctions is governed by a combination of the macroscopic quantum coherence of superconducting systems and the mesoscopic physics inherent to semiconducting devices and Andreev bound states are the microscopic states which mediate transport through these junctions. In this thesis a series of experiments aimed at understanding Andreev bound states in Josephson junction devices are presented. RF reflectometry measurements of a superconducting tunnel junction are made sensitive near the high tunnel resistance by an impedance transforming tank circuit which can be adapted for different device resistances. The reflectometry measurement corresponds well with DC transport data meaning this technique can measure Josephson junction dynamics at high frequency. Progress is made towards more transparent superconducting contacts to CVD graphene for graphene Josephson junctions however switching to an epitaxial Al / InAs 2DEG material bypasses the contact transparency issue. Signatures of transport mediated by Andreev bound states in the few mode regime are observed in quantum point contact devices made from this material allowing the possibility of controlling and measuring single Andreev bound states. Josephson junctions coupled to superconducting resonators are measured using microwave frequency detection and DC transport. Andreev bound states in the few mode regime are observed via their effect on the resonator frequency suggesting that Andreev bound states in this material can be coupled to a resonator allowing measurement and control.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2019

Author dc:creator

• Chidambaram, Vivekananth

Advisors dc:contributor.advisor

• Connolly, Malcolm
• Smith, Charles

• Superconductor - Semiconductor Junctions
• Andreev Bound States
• Transport
• Circuit QED

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6d1faf04-2ce4-4b29-8853-f50a050517de/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.53209

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/306130