Université de Liège, Belgium

报告摘要：

Superconducting resonators are essential components in quantum circuits and highly sensitive sensors. However, their performance is often compromised by magnetic flux penetration, as the interaction of flux quanta and the induced radio-frequency (RF) currents in the superconducting thin film leads to significant energy dissipation. At low operating temperatures, this issue is aggravated as thermomagnetic instabilities can trigger the sudden propagation of magnetic flux avalanches. An important open question is whether the RF excitation itself stimulates the nucleation and propagation of magnetic flux avalanches in the superconducting thin film. The literature remains inconclusive on this point, partly due to the lack of compelling evidence for this phenomenon. In this presentation, we address this challenge by directly visualizing magnetic flux penetration through Faraday rotation imaging under simultaneous RF excitation. We demonstrate that the avalanche activity exhibits a weak dependence on the RF intensity. However, magnetic flux bursts clearly influence the RF transmission properties of the device. Furthermore, we can unambiguously associate a particular avalanche event with a jump in resonance frequency. This enables us to identify the loci of most deleterious events and understand the distinct origins of upward and downward frequency shifts. These observations are supported by electromagnetic simulations in which local changes of the kinetic inductance mimic flux avalanches and confirm the invasive character of the MOI technique. The insights gained from this study aim to contribute to the broader understanding of the magnetic resilience of superconducting resonators, to improve their efficiency and stability.

In collaboration with Julia Baumgarten, Nicolas Lejeune, Lukas Nulens, and Joris Van de Vondel.

报告人简介：

Alejandro Silhanek is a full professor of Department of Physics, Faculty of Sciences at the University of Liège, Belgium. He holds a master degree in physics from the University of La Plata, Argentina, and a Ph.D. degree in Physics obtained from Instituto Balseiro, Bariloche (Argentina) in 2001. He was awarded Directors funded Postdoctoral fellow, Los Alamos National Laboratory (USA) from 2004 to 2006 and Postdoctoral Researcher FWO (Belgium) from 2006 to 2011. The scientific activities of his group are mainly within the field of experimental mesoscopic physics, nanoscience and nanotechnology, magnetism, superconductivity, and quantum transport.

地点：M236会议室

联系人：朱北沂 副研究员