Ultra-fast vortex motion in a direct-write Nb-C superconductor

Abstract

The ultra-fast dynamics of superconducting vortices harbors rich physics generic to nonequilibrium collective systems. The phenomenon of flux-flow instability (FFI), however, prevents its exploration and sets practical limits for the use of vortices in various applications. To suppress the FFI, a superconductor should exhibit a rarely achieved combination of properties: weak volume pinning, close-to-depairing critical current, and fast heat removal from heated electrons. Here, we demonstrate experimentally ultra-fast vortex motion at velocities of 10–15 km s−1 in a directly written Nb-C superconductor with a close-to-perfect edge barrier. The spatial evolution of the FFI is described using the edge-controlled FFI model, implying a chain of FFI nucleation points along the sample edge and their development into self-organized Josephson-like junctions (vortex rivers). In addition, our results offer insights into the applicability of widely used FFI models and suggest Nb-C to be a good candidate material for fast single-photon detectors.

Interaction between moving Abrikosov vortices in type-II superconductors

“…If this is the case, the crossover velocity v c ∝ 1/σ could be suppressed and high values of the reduced velocity u = v/v c become available. In experiments [1,2], at velocities exceeding 10 6 cm/s, vortices are reported to form chains along the velocity. The moving vortex core has a tail of suppressed order parameter in the −v direction which at large enough velocities may cause the following vortex to trail the first one.…”

“…It is worth noting that large values of the reduced velocity u = v/v c not necessarily imply a large actual velocity because v c depends on temperature, in particular, v c → 0 when T → T c . For a "fast" motion u 2 1, Eq. 11gives…”

“…Recent experiments have tracked Abrikosov vortices moving with extremely high velocities well exceeding the speed of sound [1,2]. The time-dependent Ginzburg-Landau equations (GL) were the major tool used to model vortex motion.…”

Writing 3D Nanomagnets Using Focused Electron Beams

“…Remarkably, Nb-C-FIBID exhibits a rare combination of properties: weak volume pinning, close-to-depairing critical current and fast heat removal from heated electrons. This provides access to investigations of vortex dynamics at >10 km/s vortex velocities [ 135 ] and renders Nb-C-FIBID as a candidate material for single-photon detectors, with properties comparable to NbN and MoSi thin films [ 136 , 137 ]. In addition, the direct-write capability of FIBID and FEBID should be fortunate for on-chip and on-fiber detector integration in circuits for quantum information processing.…”

Direct-Write Printing of Josephson Junctions in a Scanning Electron Microscope

“…Given the widespread availability of electron microscopes, the EBID approach presented here provides an accessible and relatively inexpensive means to fabricate Josephson devices such as SQUIDs and single-photon detectors. 26 The ability to directly print a Josephson junction on a given surface, without the use of energetic ions or wet processing, expands the current applications of superconducting electronics. This is particularly advantageous when dealing with nonplanar surfaces, mechanically fragile substrates ( e.g.…”