Current dependence of the negative magnetoresistance in superconducting NbN nanowires

Abstract

Magnetoresistance measurements in amorphous NbN nanowires show that transport current affects their negative magnetoresistance (nMR) in a manner qualitatively similar to temperature. In particular, the current suppresses the nMR and, beyond a certain level it eliminates the effect altogether. As the temperature dependence of the nMR effect is more pronounced at low currents, similarly the current dependence of the effect is more pronounced at low temperatures. These results are discussed in terms of the phenomenological model which attributes the nMR to the interplay between the resistance originating from the rate of phase slips via the Josephson relation and the Ohmic contribution from quasiparticles charge imbalance that accompany fluctuations of the order parameter in the nanowire.

Current–voltage characteristics of focused ion beam fabricated superconducting tungsten meanders

“…The occurrence of PS features [22][23][24][25][26][27][28][29][30] is generally attributed to the fluctuation of condensate wave function due to the spatial and temporal restrictions of the dimensional limitations or phase fluctuations in a superconducting system with reduced dimensions of the order of coherence length (x). Nevertheless, the PS features in the form of TAPS [23,[29][30][31] and QPS [24,25,[31][32][33] have been observed even for systems [18,[26][27][28][34][35][36] with physical dimensions higher than the coherence length. An interested reader may find that there are a number of reports, [18,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] in which the PS signatures in the form of TAPS, QPS in resistance-temperature transition below T C and intermediate resistive steps (IRS) in current-voltage characteristics (IVC) were reported for different nanostructures fabricated by FIB and other techniques.…”

“…Nevertheless, the PS features in the form of TAPS [23,[29][30][31] and QPS [24,25,[31][32][33] have been observed even for systems [18,[26][27][28][34][35][36] with physical dimensions higher than the coherence length. An interested reader may find that there are a number of reports, [18,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] in which the PS signatures in the form of TAPS, QPS in resistance-temperature transition below T C and intermediate resistive steps (IRS) in current-voltage characteristics (IVC) were reported for different nanostructures fabricated by FIB and other techniques. These PS features may evolve with respect to external parameters such as-magnetic field and temperature and can get suppress after a certain limit values.…”

“…Nevertheless, we have observed IRS states in the IVC with respect to temperature and magnetic field for all the wires having individual wire width of 240 nm, 640 nm and 850 nm. This observation has prompted us to invoke the TAPS and QPS mechanisms which are widely reported for superconducting nanowires [23][24][25][29][30][31][32] for the observed residual resistance below the T C as function of temperature. The general superconducting properties such as T , C B , C2 and x of the MW wires under the current investigation are in comparison to our earlier reports on FIB deposited W [18,20] as well as with respect to the reports from other groups [13,[15][16][17][18][19][20].…”