Where is the traditional technology 15km?

Scientists have discovered a new superconducting system, in which the magnetic flux can move at the speed of 10 to 15 km/s, which provides a method for studying the rich physics of unbalanced collective systems and makes the direct-writing Nb-C superconductor a candidate material for single-photon detectors. The research results were published in the journal Nature Communications. Superconduction is a physical phenomenon of many materials at low temperature, which shows that the resistance disappears and the magnetic field is discharged from the inside of the material.

Superconductors have been used in medical imaging, fast digital circuits or sensitive magnetometers, and have great potential for further application. However, the conductivity of most superconductors with important technical value is actually not 100%. In these so-called superconductors of the second kind, the external magnetic field penetrates the material in the form of magnetic lines. These flux lines are called Abrikosov Vortex, named after the prediction of physicist Alexei Abrikosov, and won the 2003 Nobel Prize in Physics.

At moderate current, the eddy current begins to move, and the superconductor can no longer carry current without resistance. In most superconductors, the low resistance state is limited by the vortex speed of 1 km/s, which determines the practical use limit of superconductors in various applications. At the same time, this speed is not enough to solve the rich physical problems of unbalanced collective systems. Now, a team of scientists from Vienna University, Goethe University in Frankfurt and RAS Institute of Microstructure have discovered a new superconducting system.

In this new superconducting system, the magnetic flux can move at the speed of 10 to15 km/s. This new superconductor shows a rare performance combination-high structural uniformity, large critical current and rapid relaxation of heated electrons. The combination of these characteristics ensures that the sudden transition of flux (flow instability) superconductors from low resistance state to normal conduction state occurs at a sufficiently large transmission current. Oleksander Dobrovolschi, the lead author of this study and director of the Superconducting and Spintronics Laboratory of Vienna University, said:

In recent years, experimental and theoretical work has pointed to a noteworthy problem. Some studies suggest that current-driven eddy currents may move faster than superconducting carriers. However, these studies use locally inhomogeneous structures. Although the intrinsic pinning in these materials is not necessarily as weak as that in other amorphous superconductors, the rapid relaxation of heated electrons becomes the main factor to make ultrafast vortex motion. In this study, researchers made an Nb-C superconductor by focused ion beam induced deposition at Goethe University in Frankfurt.

It is worth noting that in addition to the ultra-fast vortex speed of Nb-C superconductors, direct writing nano-fabrication technology can also manufacture nanostructures with complex shapes and three-dimensional magnetic flux loops with complex interconnections, which may be applied to quantum information processing. In order to achieve the maximum current that superconductors can carry, that is, the so-called de-pairing current, it needs to be quite uniform in the macro-length range, which is partly due to small defects in materials. It is not only a basic problem, but also very important for application to realize the de-alignment current. As predicted and confirmed by the experiment:

If the micron-wide superconducting tape is biased by a current close to the current value, the tape can be transformed into a resistance state by a single near-infrared or optical photon. Denis Vodolazov, a senior researcher at RAS Institute of Microstructure, said: This method opens up a prospect for building a large-area single-photon detector, which can be used in * * * focal microscope, free-space quantum cryptography, deep-space optical communication and other fields. Researchers have successfully studied the moving speed of eddy current in the deposited Nb-C superconducting tape. The critical current of these superconducting tapes is close to the depolarization current, and the magnetic field is zero.

The results show that the flux flow instability begins near the edge of superconductor due to the locally enhanced current density. This provides insights into the applicability of the widely used flux instability model, and shows that Nb-C superconductors are good candidates for fast single photon detectors.