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

Abstract

We report magneto-transport measurements on a superconducting molybdenum-germanium (MoGe) film of thickness d=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 T > Tv (B). Here Tv appears to match the vortex core explosion condition d ≈ 4.4ξ(Tv), where ξ is the coherence length. For T > Tv, we observed that a nonlinear current-voltage (IV ) response (Ohmic at low currents and the power law V ∝ I β at higher I) is exponentially dependent on B 2 . We propose a model in which the resistive state at T > Tv is due to thermally-activated hopping of spontaneous perpendicular vortices tuned by the pairbreaking effect of the parallel B.

Current driven vortex-antivortex pair breaking and vortex explosion in the Bi2Te3/FeTe interfacial superconductor

“…The result is shown in Fig. 3, which clearly shows a break below at T v = 5.7 K, similar to what was previously observed in MoGe [10]. To qualitatively understand this observation, we first note that the conditions of temperature (T T BKT ) and current (I 3.67, 3.72, 3.92, 4.22, 4.59, 5.01, 5.46, 5.96, 6.47, 6.98, 7.76, 8.56, 9.31, 10.10, 11.00, 12.99, 14.09, 15.26, 16.57, 18.00, 19.34, 20.78, and 22.34 K. that the BKT mechanism will not provide appreciable dissipation (negligible population of unbound vortex-antivortex pairs).…”

“…The second scenario, the edge nucleation of single vortices as proposed recently by Gurevich and Vinokur (GV) [9], can become a dominant source of dissipation under certain conditions (e.g., somewhat outside the 2D limit ξ > d and for T < T BKT ) for which the BKT dissipation is suppressed. As shown previously [10], the GV edge nucleation process is in turn facilitated when parallel vortex segments are precluded by the Likharev vortex explosion phenomenon [11]. The gist of the Likharev phenomenon is that a stable vortex core can exist inside a film along the direction parallel to the film only if there is a minimum thickness d ≥ 4.4ξ(T ).…”

“…Our previous work on thin molybdenum-germanium (MoGe) films [10] provided the first experimental confirmation of this prediction.…”

“…In this case the small amount of residual resistance will arise mainly through the GV process (unbinding of edge nucleated vortices from their antivortex images outside the edge). The GV mechanism is facilitated by the Likharev exploded vortex condition [10], and thus the resistance is expected to decrease more rapidly below the vortexexplosion transition temperature T v .…”

Current-induced depairing in theBi2Te3/FeTeinterfacial superconductor

“…A rough estimate of the current level required to promote penetration of a vortex at the film edge can be obtained from the energy balance between the work of the Lorentz force ≃ IΦ 0 d/2w to form a vortex semi-loop of diameter equal to the film thickness d at the edge 11 , and the self-energy of the vortex ≃ Φ 2 d/4πµ 0 λ 2 at the film edge 12 . The condition…”