Tunable domino effect of thermomagnetic instabilities in superconducting films with multiply-connected topological structures

Abstract

Topology is a crucial ingredient for understanding the physical properties of superconductors. Magnetic field crowds to adopt the form of a topologically-protected quantum flux lines which can lose this property when moving at high velocities. These extreme conditions can be realized when superconductors undergo a thermomagnetic instability for which the sample topology come also into play. In this work, utilizing the magneto-optical imaging technique, we experimentally study magnetic flux avalanches in superconducting films with multiply-connected geometries, including single and double rings. We observe a domino effect in which avalanches triggered at the outer ring, stimulate avalanches at the inner ring thus impairing the expected magnetic shielding resulting from the outer ring and gap. We implement numerical simulations in order to gain more insight into the underlying physical mechanism and demonstrate that such event is not caused by the heat conduction, but mainly attributed to the local current distribution variation near the preceding flux avalanche in the outer ring, which in turn has a ripple effect on the local magnetic field profile in the gap. Furthermore, we find that the domino effect of thermomagnetic instabilities can be switched on/off by the environmental temperature and the gap width between the concentric rings. These findings provide new insights on the thermomagnetic instability in superconducting devices with complex topological structures, such as the superconductor-insulator-superconductor (SIS) multilayer structures of superconducting radio-frequency (SRF) cavities.

Sensitivity of the thermomagnetic instability in superconducting film to magnetic perturbation for electromagnetic interference detection

“…In this paper, all simulations are implemented using a DC field of this ramp rate. Since the actual electric field can be much larger than that obtained from the simple theoretical calculation due to the strong nonuniformity of the flux penetration both in space and in time, the ramp rates that trigger the thermomagnetic instability are much smaller in experiments [22,34,[55][56][57]. We also show the flux distribution of the films when the magnetic field increases linearly to the same field B a = 8 mT for comparison (see figures 2(d-f)).…”

Effects of edge cracks on the thermomagnetic instabilities of type-II superconducting thin films

“…Recent MOI observations and numerical simulations have revealed that random or structured defects significantly affect the TMI behavior of SC thin films [ 25–30 ]. Within inhomogeneous SC films patterned with arrays of antidots [ 25 , 26 , 28 ], blind holes [ 27 , 29 ] and insulating particles [ 30 ], it is found that inhomogeneities strongly modify the current carrying capacity and dramatically change the flux avalanche patterns. Quantitative MOI measurements of the vortex avalanches in SC films show that the probability distributions of avalanche sizes follow power laws and demonstrate finite-size scaling [ 31 , 32 ].…”