Current-voltage characteristic of narrow superconducting wires: bifurcation phenomena

The current-voltage characteristics of long and narrow superconducting channels are investigated using the time-dependent Ginzburg-Landau equations for complex order parameter. We found out that the steps in the current voltage characteristic can be associated with bifurcations of either steady or oscillatory solution. We revealed typical instabilities which induced the singularities in current-voltage characteristics, and analytically estimated period of oscillations and average voltage in the vicinity of the critical currents. Our results show that these bifurcations can substantially complicate dynamics of the order parameter and eventually lead to appearance of such phenomena as multistability and chaos. The discussed bifurcation phenomena sheds a light on some recent experimental findings

NbS3_{3}: A unique quasi one-dimensional conductor with three charge density wave transitions

Through transport, compositional and structural studies, we review the features of the charge-density wave (CDW) conductor of NbS$_{3}$ (phase II). We highlight three central results: 1) In addition to the previously reported CDW transitions at $T_{P1}$ = 360\,K and $T_{P2}$ = 150\,K, another CDW transition occurs at a much higher temperature $T_{P0}$ = 620-650\,K; evidence for the non-linear conductivity of this CDW is presented. 2) We show that CDW associated with the $T_{P2}$ - transition arises from S vacancies acting as donors. Such a CDW transition has not been observed before. 3) We show exceptional coherence of the $T_{P1}$-CDW at room-temperature. Additionally, we report on the effects of uniaxial strain on the CDW transition temperatures and transport.Comment: 16 pages, 18 figure