arXiv subjects

B. Biehler

Publications and source records attributed to B. Biehler.

2 recordsLinked to original sources

arXiv2004

Observation of a New Mechanism of Spontaneous Generation of Magnetic Flux in a Superconductor

We report the discovery of a new mechanism of spontaneous generation of a magnetic flux in a superconductor cooled through $T_c$. The sign of the spontaneous flux changes randomly from one cooldown to the next, and follows a Gaussian distribution. The width of the distribution increases with the size of the temperature gradient in the sample. Our observations appear inconsistent with the well known mechanisms of flux generation. The dependence on the temperature gradient suggests that the flux may be generated through an instability of the thermoelectric superconducting-normal quasiparticle counterflow.

cond-mat.supr-con↗

arXiv2004

On ultrafast magnetic flux dendrite propagation into thin superconducting films

We suggest a new theoretical approach describing the velocity of magnetic flux dendrite penetration into thin superconducting films. The key assumptions for this approach are based upon experimental observations. We treat a dendrite tip motion as a propagating flux jump instability. Two different regimes of dendrite propagation are found. A fast initial stage is followed by a slow stage, which sets in as soon as a dendrite enters into the vortex-free region. We find that the dendrite velocity is inversely proportional to the sample thickness. The theoretical results and experimental data obtained by a magneto-optic pump-probe technique are compared and excellent agreement between the calculations and measurements is found.

cond-mat.supr-con↗