Physicists have discovered a novel resonant oscillation of superconducting critical currents associated with tunneling between local Andref's quantum energy levels. They were found in the Josephson junction made of single nanocrystals based on topological insulators. It turns out

Physicists have discovered a novel resonant oscillation of superconducting critical currents associated with tunneling between local Andref's quantum energy levels. They were found in the Josephson junction made of single nanocrystals based on topological insulators. It turns out that nanocrystals are not only promising in studying the basic physical processes in mesoscopic quantum systems, but are also generally conducive to the development of quantum technology.

Results of this work published in the highly rated international scientific journal Advanced Quantum Technologies. Mesometric devices based on topological insulators are real scientific Klondike, and scientists are looking for and are still looking for many new foundations and application effects. As you already understand from the name, this type of material is often called an insulator, or something else - not allowing current to pass through its own dielectric or semiconductor. But there is one very important exception: In its thinnest surface, this material conducts current like metal.

Briefly, you can imagine topological insulator as fragments of a tree covered with copper on both sides. However, in this case, we are not talking about two substances, but about homogeneous samples of the same material. In addition, this material is a special quantum state of electrons in the surface layer so that they are not only current carriers, but also "topologically protected" carriers.

This characteristic is due to the fact that these quantum states of electrons are very stable—unlike the ordinary electron states in metals, they are more stable when interacting with the atom defects, steps or other defects of the material.

Scientists from the Moscow Institute of Physics and Technology discovered a novel superconducting critical current resonance oscillation in a new Josephson device created by the research team based on topological insulator nanocrystals.

Vasily Stolyarov, Director of the Center for Physical and Nanotechnology Methods Research in MIPT Advanced Middle School

"We discovered a novel oscillation of the critical current of the Josephson junction, which consists of two superconducting niobium electrodes, and a hexagonal Bi2Te2.3Se0.7 topological insulator nanocrystals are placed between these two electrodes. The oscillation occurs in the temperature range of 400 to 20 mK (–272.7 °C) and has a very unusual pointed shape.

The period of these oscillations is only 1 Oster, with a corresponding energy scale of 1 μeV. We found that the observed effect could be due to resonant tunneling of Andrev quasi-particle between energy levels formed near the superconductor/topotopic insulator boundary,” said Vasily Stolyarov, head of the research and director of the Advanced Methods Center for Medium Physics and Nanotechnology. MIPT.

experiment was performed on BlueFors LD250 diluted refrigerator. For such precision research, a method developed by one of the co-authors for filtering electrons and thermal noise was used.

According to the developers, the oscillating peak shape and its wide temperature range of ultra-short cycles appearing are direct experimental evidence, indicating that the materials studied can serve as a platform for realizing future quantum devices.

"I want to point out that we are the first person in the world to decide to implement the Josephson device on a separate nanocrystal of topological insulators, and that's the result. I think there is a bright future for equipment in such facilities," Vasily Stolyarov added.

Topological protection of electronic subsystems of such materials can lead to record resistance of such devices to decoherent sources, thus making calculations more accurate than the physics currently used in the "classic" quantum bits.

As co-authors of this work reported, the next phase of the study will be research on improving nanocrystal synthesis technology, techniques for making direct superconducting devices, and how to effectively control quasi-superconducting devices. - Particle Andreev level and how to implement quantum logic devices based on them.

"Our results have very important fundamental significance, as there has been no previous prediction of the presence of Andlev energy levels in systems with superconductor/topotopic insulator boundaries.Furthermore, since the energy scale of such energy level systems is very small, it is impossible to consider conducting exemplary electron transmission experiments. In this case, multiple situations allow us to do this,” concluded Vasily Stolyarov.

This work was supported by the Russian Science Foundation. In addition to the scientists at the Moscow Institute of Physics and Technology Center for Advanced Methods and Nanotechnology, they also participated in the work from the Sorbonne University (Paris) Superconducting Metamaterials MISiS Laboratory, Institute of Microelectronics Technology, Russian Academy of Sciences, Institute of Solid State Physics, and Twente University ( Netherlands ) in the work.