Flux avalanches triggered by microwave depinning of magnetic vortices in Pb superconducting films

Abstract

We observe abrupt changes in broadband microwave permeability of thin Pb superconducting films as functions of the microwave frequency and intensity, as well as of external magnetic field. These changes are attributed to vortex avalanches generated by microwave induced depinning of vortices close to the sample edges. We map the experimental results on the widely used theoretical model assuming reversible response of the vortex motion to ac drive. It is shown that our measurements provide an efficient method of extracting the main parameter of the model-depinning frequencies-for different pinning centers. The observed dependences of the extracted depinning frequencies on the microwave power, magnetic field, and temperature support the idea that the flux avalanches are generated by microwave induced thermomagnetic instabilities.

Dual cut-off direct current-tunable microwave low-pass filter on superconducting Nb microstrips with asymmetric nanogrooves

“…The dynamics of Abrikosov vortices at mw frequencies has been extensively studied both theoretically [18][19][20][21][22][23] and experimentally 6,9,10,[14][15][16][17][18][24][25][26][27][28] . The central notion in the theoretical treatment of the ac-driven vortex dynamics is the depinning frequency 18,24 .…”

“…It is defined as the frequency separating the low-frequency regime where the pinning forces dominate and the vortex response is weakly dissipative, from the high-frequency regime where the frictional forces prevail and the response is strongly dissipative. On the experimental side, the mw-driven vortex dynamics has been studied in low-T c [14][15][16]18,[25][26][27][28] and high-T c 10,17,24 superconductors. Among these, a notable part of the work was concerned with nanopatterned superconductors 6,[15][16][17]28 for which advanced fluxonic device functionalities are anticipated and, under certain conditions, a stimulation of superconductivity by a GHz stimulus has been observed recently 28 .…”

“…Unless pinned, they increase noise and bit error rate in quantum interference devices (SQUIDs) 11 , raise unwanted vortex-assisted photon-count rates in detectors 12 , and reduce quality factors 5,6 and power handling capabilities 13 . In addition, depinning of vortices has been shown to trigger flux avalanches close to the edges of coplanar waveguides (CPWs) 14 . At the same time, several approaches to reduce microwave (mw) losses have been proposed.…”

Local mapping of dissipative vortex motion

“…22 This dissipative process has a typical short characteristic time of the order of, τ p = η/α L 0.1 μs. 23,29 For the applied low driving frequency, f = 77.123 Hz, the restoring force dominates over the viscous drag force, as ω 1/τ p , and this term can be neglected. The term i/ωτ 1 is related to thermally activated vortex hopping across an effective activation barrier, following the classic ideas of Anderson and Kim 30 and results from ξ (t) in Eq.…”

Avalanche-like vortex penetration driven by pulsed microwave fields in an epitaxial LaSrCuO thin film

“…9 Vortex instabilities have been also observed in the microwave (MW) response of MgB 2 resonators as jumps in the resonance curves of the frequency-dependent complex transmission coefficient. 16,17 Recently, vortex avalanches in Pb and Nb superconducting films, induced respectively by vortex depinning 18 and ac magnetic fields, 19 have been reported. In the former, the avalanche was triggered at the edge by rising the temperature locally while in the latter it appears as a result of a train of ac field cycles.…”