Magnetic fields as a tool to control superconducting devices

Dr. Davi Chaves
(DF/UFSCar)

Resumo:

Superconductors are at the forefront of an ongoing technological revolution. The emergence of novel computing schemes working at cryogenic temperatures has urged the development of new superconducting devices. Our research aims to explore the interaction between applied magnetic fields and superconducting thin films to provide avenues to control important features of such devices. A common thread in our works is to employ magneto-optical imaging (MOI) to visualize the local distribution of magnetic flux in the studied materials in real-time. In this presentation, I will discuss some of our recent results: (i) I will demonstrate how cooling under inhomogeneous magnetic fields may increase superconducting critical currents without requiring any nanostructuring process; (ii) We studied the effects of a single nanometric-deep weak-link on the superconducting and normal states’ properties of a prototypical niobium film; (iii) A quantitative MOI study allowed us to reveal how magnetic fields can be used to modify the expected weak-link behavior to that of a strong-link, drastically increasing the critical current density at particular fields. This is a tunable phenomenon that may have an immediate impact on superconducting devices; (iv) We have investigated the interaction of an applied magnetic field with a superconducting film presenting a nanoscale thickness gradient, revealing how the induced critical current modulation impacts the device’s response; (v) Lastly, I will introduce a magnetic field-assisted protocol that enables access to several memory states of nanobridge SQUIDs and demonstrate how these devices may work as superconducting multilevel memory elements.

Departamento de Física dos Sólidos
Instituto de Física UFRJ