Negative differential resistivity in superconductors with periodic arrays of pinning sites

TL;DR

This paper theoretically investigates how heating affects magnetic flux flow in superconductors with periodic pinning sites, revealing the emergence of negative differential resistivity types and resulting instabilities leading to complex flux dynamics.

Contribution

It introduces a theoretical analysis of NDR effects in superconductors with PAPS, highlighting the coexistence of N- and S-type NDR and their impact on flux flow instabilities.

Findings

Superconductors with PAPS exhibit S- and N-type NDR in their VI-curves.

S-type NDR leads to filamentary flux flow instability.

Moderate disorder in pinning sites does not alter NDR effects, but strong disorder suppresses S-type NDR.

Abstract

We study theoretically the effects of heating on the magnetic flux moving in superconductors with a periodic array of pinning sites (PAPS). The voltage-current characteristic (VI-curve) of superconductors with a PAPS includes a region with negative differential resistivity (NDR) of S-type (i.e., S-shaped VI-curve), while the heating of the superconductor by moving flux lines produces NDR of N-type (i.e., with an N-shaped VI-curve). We analyze the instability of the uniform flux flow corresponding to different parts of the VI-curve with NDR. Especially, we focus on the appearance of the filamentary instability that corresponds to an S-type NDR, which is extremely unusual for superconductors. We argue that the simultaneous existence of NDR of both N- and S-type gives rise to the appearance of self-organized two-dimensional dynamical structures in the flux flow mode. We study the effect of the pinning site positional disorder on the NDR and show that moderate disorder does not change the predicted results, while strong disorder completely suppresses the S-type NDR.