Current-Voltage Characteristics of Quasi-One-Dimensional Superconductors: AnS-Shaped Curve in the Constant Voltage Regime

Abstract

Applying a constant voltage to superconducting nanowires we find that its IV-characteristic exhibits an unusual S-behavior. This behavior is the direct consequence of the dynamics of the superconducting condensate and of the existence of two different critical currents: jc2 at which the pure superconducting state becomes unstable and jc1 < jc2 at which the phase slip state is realized in the system. PACS numbers: 74.25. Op, 74.20.De, The majority of the experiments on the resistive state in quasi-one dimensional systems were performed in the constant current regime and at temperatures close to T c . It is extremely difficult to apply voltage to a superconductor because the current density induced by the applied electric field inevitably reaches the critical value and destroys superconductivity in the sample. The decrease of the superconducting current by the appearance of phase slip centers [1,2,3,4,5] is not effective in this case because of the large heating of the sample at low temperatures. At temperatures close to T c the heating can be suppressed due to the low value of the critical currents but in this case the applied electric field does not penetrate deep into the sample because of the existence of regions near the N-S boundary where the drop of the applied voltage occurs [6,7].This situation drastically changes with the appearance of nano-technology and the ability to create long (to allow the appearance of phase slip centers) superconducting wires with a small cross section (to decrease the effect of heating). In this Letter we present results on the behavior of such nanowires in the constant voltage regime. We found that the I-V characterestic in this case has a remarkable S-shape. Our theoretical analysis based on the time-dependent Ginzburg-Landau equations (TDGL) shows that such a behavior is a direct consequence of the dynamics of the superconducting condensate and we predict new unusual features which still need additional experimental study.The superconducting nanowires were prepared by electrodeposition into nanopores of homemade track-etched polycarbonate membranes [8]. For the lead nanowires, a 22 µm thick membrane (with pore diameter ∼ 40 nm and pore density ∼ 4·10 9 cm −2 ) and an aqueous solution of 40.4 g/l Pb(BF 4 ) 2 , 33.6 g/l HBF 4 and 15 g/l H 3 BO 3 were used [9], while in the case of the tin nanowires, a 50 µm thick membrane (with pore diameter ∼ 55 nm and pore density ∼ 2·10 9 cm −2 ) and an electrolyte of 41.8 g/l Sn(BF 4 ) 2 in water solution were applied. Constant potential of -0.5 V versus an Ag/AgCl reference electrode was used in a three-electrode configuration in order to reduce the Pb 2+ or Sn 2+ ions into the nanopores. As shown in Fig. 1, the nanowires are cylindrical and the diameter is uniform along their length. In order to perform elec-

Influence of High Magnetic Fields on the Superconducting Transition of One-Dimensional Nb and MoGe Nanowires

“…We observe that at high currents the wires undergo a transition into resistive state. This transition is smooth at high temperatures and it is jumpwise, with some hysteresis, at low temperatures [4,14] (Fig. 2a).…”

Selective epitaxial growth of submicron complex oxide structures by amorphous SrTiO3

“…Both the discontinuity of the voltage in the V -I characteristic and the s-shaped I-V characteristic of the microstrip are consistent with phase-slip behavior due to the lateral confinement of the superconductor. [24,25] An investigation of the phase-slip behavior in our YBCO microstrips as well as information derived from such behavior on the dynamics of the superconducting order parameter is the focus of separate papers. [26,27] Sub-micron LCMO strips were also fabricated using our technique.…”

Inhomogeneous state in nonequilibrium superconductor/normal-metal tunnel structures: A Larkin-Ovchinnikov-Fulde-Ferrell-like phase for nonmagnetic systems

“…This type of the CVC may also occur in semiconductors [31] as a result of the so-called overheating mechanism and in bulk superconductors in the presence of a dissipative current [10,11,26,29]. This phenomenon is possible for a special dependence of the heat source J(V, T ) and heat absorption term S(T ) on the effective temperature T and applied voltage V. The "N-shaped" CVC may also arise as a result of the overheating mechanism [12,21,23,24,25].…”

“…The calculated I-V characteristics (CVC) was shown to be of the so-called N-shape type, that is, three values of voltages correspond to one value of the bias current I b . Earlier this type of the I-V characteristics was studied in other superconducting systems [12,23,24,25].…”