Stroboscopic phenomena in superconductors with dynamic pinning landscape

Datum: 23 november 2016

Locatie: University of Antwerp - Campus Groenenborger - Room U.241 - Groeneborgerlaan 171 - 2020 Antwerpen (route: UAntwerpen, Campus Groenenborger)

Tijdstip: 16 - 17 uur

Organisatie / co-organisatie: Condensed Matter Theory

Korte beschrijving: Condensed Matter Theory seminar presented by Zeljko Jelic

Introducing artificial pinning centers is a well-established strategy to trap quantum vortices and increase the maximal magnetic field and applied electric current that a superconductor can sustain without dissipation. In case of spatially periodic pinning, a clear enhancement of the superconducting critical current arises when commensurability between the vortex configurations and the pinning landscape occurs. With recent achievements in (ultra-fast) optics and nano-engineered plasmonics it has become possible to exploit the interaction of light with superconductivity and create not only spatially periodic imprints on the superconducting condensate, but also temporally periodic ones.

Here we show that in the latter case, temporal matching phenomena develop, caused by stroboscopic commensurability between the characteristic frequency of the vortex motion under applied current and the frequency of the dynamic pinning. The matching resonances persist in a broad parameter space, including magnetic field, driving current, or material purity, giving rise to unusual features such as externally variable resistance/impedance and Shapiro steps in current-voltage characteristics. As one of the possible applications for the stroboscopic effect, we devised a method combining conventional transport measurements and a frequency-tuned flashing pinning potential to obtain reliable estimates of the vortex velocity. We discuss the sensitivity of the proposed technique on applied current, temperature and heat diffusion, as well as the vortex core deformations during fast motion.

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