Department of Particle Physics and Astrophysics

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Events

Colloquia

May 29, 2019
Edna and K.B. Weissman Building of Physical Sciences Auditorium
Vortices in superconducting arrays: probing dissipation and interactions
Prof. Nadya Mason
UIUC

Event Information

Title:
Vortices in superconducting arrays: probing dissipation and interactions
Details:
UIUC11:00 – coffee, tea, and more
Lecturer:
Prof. Nadya Mason
Date:
May 29, 2019
Time:
11:15:00 - 12:30:00
Location:
Edna and K.B. Weissman Building of Physical Sciences Auditorium
Abstract:
Superconductivity continues to be an exciting and fertile field of research, with potential applications in energy efficiency and storage. Non-superconducting systems in contact with superconductors have been of particular recent interest, as these proximity-coupled superconductors may show new behaviors or harbor unusual excitations (eg, Majoranas in topological-superconductor systems). A key to understanding and utilizing superconductors is understanding their behavior in magnetic fields, particularly when the field penetrates as quantized tubules of flux, or vortices. In this talk I will show that, although vortices have been studied for many years, measurements of their current-driven dynamics can still lead to new results and understanding. I will discuss transport measurements of current-driven vortices in superconductor-normal-superconductor (SNS) arrays, where we are able to access a number of vortex regimes, and find unusual behavior in the non-equilibrium transitions between vortex states. First, in the low magnetic field regime, we find that the dynamic behavior of vortices is consistent with the presence of time delayed dissipative forces. I will also discuss how at higher magnetic fields, vortex de-pinning occurs in two steps, consistent with a commensurate lattice appearing even for non-commensurate magnetic field values. This two-step behavior is due to strong vortex interactions, and has not previously been observed. Finally, I will discuss measurements of vortex arrays on topological insulators, where we see enhanced dissipation and evidence of unusual charged vortices, predicted as the “Witten effect” in topological systems.