Negative magnetoresistance and phase slip process in superconducting nanowires

We argue that the negative magnetoresistance of superconducting nanowires, which was observed in recent experiments, can be explained by the influence of the external magnetic field on the critical current of the phase slip process. We show that the suppression of the order parameter in the bulk superconductors made by an external magnetic field can lead to an enhancement of both the first $I_{c1}$ and the second $I_{c2}$ critical currents of the phase slip process in nanowires. Another mechanism of an enhancement of $I_{c1}$ can come from decreasing the decay length of the charge imbalance $\lambda_Q$ at weak magnetic fields because $I_{c1}$ is inversely proportional to $\lambda_Q$. The enhancement of the first critical current leads to a larger intrinsic dissipation of the phase slip process. It suppresses the rate of both the thermo-activated and/or quantum fluctuated phase slips and results in decreasing the fluctuated resistance.Comment: 7 pages, 4 figure

Fabrication and physical properties of Pb∕Cu multilayered superconducting nanowires

Using nanoporous media as templates for electrodeposition, we have fabricated multilayered Pb/Cu nanowires 50 nm in diameter and 20 μ m long with Cu layer thicknesses as low as 10 nm. This was achieved by using a single-bath technique and a precise selection of the copper deposition potential to limit the redissolution of lead when the potential is raised to electrodeposit the more noble metal. Such superconductor/normal multilayered nanowires show interesting magnetoresistance properties at a low magnetic field that may be related to the proximity effect, which can therefore be investigated in a quasi-one-dimensional geometry. (C) 2005 American Institute of Physics

Vortex detection by electrical transport measurements on a single lead nanowire under axial magnetic field

Electrical transport measurements were performed on single electrodeposited superconducting lead nanowires (330 nm diameter) by applying a magnetic field parallel to the wire axis. We observe a vortex penetration while the nanowire is in the dissipative state generated by a phase-slip center. This results in a hysteresis in the resistance-current curves. A drop of the forward critical current leads to the disappearance of this hysteresis when the magnetic field is strong enough to stabilize the vortex at zero current. While the temperature is increased, lower magnetic fields are required to stabilize this vortex. (c) 2008 American Institute of Physics

Multicontact measurements of a superconducting Sn nanowire

Multicontact transport measurements were performed on a superconducting tin nanowire to probe its local properties and especially the formation of phase-slip centers (PSCs). We find that normal metal contacts strongly disturb the behavior of the nanowire. In particular, they provide an efficient escape way for the energy dissipated at the PSC and thereby limit its size. We were able to observe PSC at 30 mK with an associated relaxation time typical to that of the inelastic scattering time for bulk normal tin. (C) 2007 American Institute of Physics

Phase-slip phenomena in NbN superconducting nanowires with leads

Transport properties of a superconducting NbN nanowire are studied experimentally and theoretically. Different attached leads (superconducting contacts) allowed us to measure current-voltage (I-V) characteristics of different segments of the wire independently. The experimental results show that with increasing the length of the segment the number of jumps in the I-V curve increases indicating an increasing number of phase-slip phenomena. The system shows a clear hysteresis in the direction of the current sweep, the size of which depends on the length of the superconducting segment. The interpretation of the experimental results is supported by theoretical simulations that are based on the time-dependent Ginzburg-Landau theory, the heat equation has been included in the Ginzbur-Landau theory