Manlai Liang

Evaluating free flux flow in low-pinning molybdenum-germanium superconducting films.

Vortex dynamics in molybdenum-germanium superconducting films were found to well approximate the unpinned free limit even at low driving forces. This provided an opportunity to empirically establish the intrinsic character of free flux flow and to test in detail the validity of theories for this regime beyond the Bardeen-Stephen approximation. Our observations are in good agreement with the mean-field result of time-dependent Ginzburg-Landau theory.

Vortex instability in molybdenum-germanium superconducting films

We studied the high driving force regime of the current-voltage transport response in the mixed state of amorphous molybdenum-germanium superconducting films to the point where the flux flow becomes unstable. The observed nonlinear response conforms with the classic Larkin-Ovchinikov (LO) picture with a quasiparticle-energy-relaxation rate dominated by the quasiparticle recombination process. The measured energy relaxation rate was found to have a magnitude and temperature dependence in agreement with theory. PACS: 74.40.Gh, 74.25.Uv, 72.15.Lh, 73.50.Gr, 73.50.Fq Keywords: fluxon, vortices, TDGL, FFF, negative differential conductivity, NDC, non-monotonic IV curve

Thermally activated dynamics of spontaneous perpendicular vortices tuned by parallel magnetic fields in thin superconducting films

We report magneto-transport measurements on a superconducting molybdenum-germanium (MoGe) film of thickness

The Mixed State of Thin Films in Parallel Fields

d

The vortex explosion transition

=50 nm in parallel magnetic fields and show evidence of a transition from a Meissner state to a resistive state of spontaneous perpendicular vortices generated by thermal fluctuations above a certain temperature

Non-linear and unstable flux vortex dynamics.

T>T_v(B)

Depairing current density of Nd2−xCexCuO4−δ superconducting films

. Here

Depairing current density of infinite-layer Sr1−xLaxCuO2 superconducting films

T_v

Vortex exclusion transition

appears to match the vortex core explosion condition

Vortex instability in molybdenum-germanium superconducting film

d\approx 4.4\xi(T_v)