Resistive Width of Superconducting Transition in Titanium Nitride Thin Film

The transition to the superconducting state of the ultrathin (5 nm thick) titanium nitride film was studied. It is found that the nonmonotonic temperature dependence of the resistance, R(T), is a consequence of competition between the contributions to conductivity from quantum corrections stemming from the electron-electron interaction in the diffusion and Cooper channels. It is shown that the appreciable decrease in the resistance at T > Tc (Tc is the superconducting transition temperature) results from the superconducting fluctuations. We present the results of the analysis of low-temperature (T < Tc ) current-voltage characteristics V(I). It is found that they follow the power-law behavior V∝ I α(T) , with α(T) increasing rapidly with the decreasing temperature. The Berezinskii-Kosterlitz-Thouless transition temperature, TBKT, and width of the superconducting transition ∆T = Tc − TБКТ were determined

Scaling of Resistivities in MgB2

Longitudinal and transverse voltages have been measured on thin films of MgB2 with different width of superconducting transition range. The study has been performed in zero and nonzero external magnetic fields. The non-zero transverse voltage has been observed in close vicinity of the critical temperature in zero external magnetic field while far enough from Tc this voltage has been zero. In magnetic field it merges into transverse voltage which is an even function with respect to the direction of the field. Usual Hall voltage starts to appear with increasing magnetic field. At the highest field the even voltage disappears and only the Hall voltage is measurable i.e. the transverse even voltage is suppressed with increasing magnetic field and increasing transport current as well. New scaling between transverse and longitudinal resistivities has been observed in the form ρxy~dρxx/dT . This correlation is valid not only in the zero magnetic field but also in nonzero magnetic field where transverse even voltage can be detected. Several models trying to explain observed results are discussed. The most promising seems to be guided motion of the vortices.