Disorder and critical current variability in Josephson junctions
Abstract
We investigate theoretically the origins of observed variations in the critical currents of Nb/Al-AlOx/Nb Josephson junctions in terms of various types of disorder. We consider the following disorder sources: vacancies within the Al layer, thickness variations in the AlOx layer, and “pinholes” (i.e., point contacts) within the AlOx layer. The calculations are all performed by solving the microscopic Bogoliubov–de Gennes Hamiltonian self-consistently. It is found that a small concentration of vacancies within the Al layer is sufficient to suppress the critical current, while the presence of a small number of thick regions of the oxide layer induces a similar effect as well. The pinhole scenario is found to result in anomalous behavior that resembles neither that of a pure tunnel junction nor that of a superconductor–normal–superconductor junction but a regime that interpolates between these two limits. We comment on the degree to which each of the three scenarios describes the actual situation present in these junctions.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 16, 2020
- Source ID
- 10.1063/1.5125765
Entities
People
- E. Patrick
- Mark E. Law
- Miguel Antonio Sulangi
- Nimesh Pokhrel
- P. J. Hirschfeld
- Thomas Weingartner
Organizations
- Division of Materials Research
- Intelligence Advanced Research Projects Activity
- University of Florida