25 research outputs found
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
NbS: 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 (phase II). We
highlight three central results: 1) In addition to the previously reported CDW
transitions at = 360\,K and = 150\,K, another CDW transition
occurs at a much higher temperature = 620-650\,K; evidence for the
non-linear conductivity of this CDW is presented. 2) We show that CDW
associated with the - transition arises from S vacancies acting as
donors. Such a CDW transition has not been observed before. 3) We show
exceptional coherence of the -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