Temperature dependence of the magnetoresistance peak in highly disordered superconductors

Abstract

Highly disordered superconductors have a rich phase diagram. At a moderate magnetic field (B) the samples go through the superconductor-insulator quantum phase transition. In the insulating phase, the resistance increases sharply with B up to a magneto-resistance peak beyond which the resistance drops with B. In this manuscript we follow the temperature (T ) evolution of this magnetoresistance peak. We show that as T is reduced, the peak appears at lower B's approaching the critical field of the superconductor-insulator transition. Due to experimental limitations we are unable to determine whether the T = 0 limiting position of the peak matches that of the critical field or is at comparable but slightly higher B. We show that, although the peak appears at different B values, its resistance follows an activated T dependence over a large T range with a prefactor that is very similar to the quantum of resistance for cooper-pairs.

New paradigm for a disordered superconductor in a magnetic field

“…On the other hand, ρ = 0 for H < Hc , develops a sharp peak at Hc and decreases gradually beyond H c . We note that in a recent experiment [28] it is claimed that the MR peak position H P → H c as T → 0, an observation consistent with our ρ in panel (e). On the other hand, for weak disorder (V = 0.5), ρ remains finite in the metal or is zero in the SC phase and leads to only a very weak hump in MR.…”

“…orders of magnitude beyond a superconductor-insulator transition (SIT). Furthermore, the lineshape of magneto-resistance (MR) ρ(H) is asymmetric [22,24] with a sharp rise to a peak at H P followed by a gradual decrease to the normal state resistance [24,28]. Interestingly, the MR-peak becomes sharper and stronger with increasing disorder in the films [23,24,29,30].…”