Condensed Matter Seminars

Conventional treatments of electronic transport predict that no metallic phase exists in two-dimensional (2D) superconducting materials at zero temperature (T=0). This view has been challenged by the observation of magnetic field (B) induced metallic behavior in amorphous MoGe and Ta thin films. We have demonstrated that the metallic phase in Ta thin films has an intrinsic origin and associates with nonlinear voltage-current (I-V) characteristics that are qualitatively different from those of superconducting and insulating phases. Based on transport measurement, we can map the phase diagram of Ta thin films in B-T-Disorder space and study the physics it reveals. We also investigated the nature of the B-induced insulating phase. We found that the peak structure of differential IV traces displayed a non-monotonic change as a function of B, which might be a signature for the localized Cooper pairs.