Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

One step closer to a new kind of computer

16.09.2015

Critical behavior at a dynamic vortex insulator-to-metal transition discovered

An international group of physicists, including Aleksandr Golubov, head of the MIPT Laboratory of Topological Quantum Phenomena in Superconductor Systems, recently presented results of experiments testing a new phenomenon in the journal Science. The results may assist scientists in the creation of an essentially new kind of electronics - Mott transition, or the transition of an insulator to a conductor.


This image shows differencial resistance.

Credit: Illustration courtesy of the researchers

Researchers from institutions in the Netherlands, Great Britain, Italy, the USA and Russia conducted a series of experiments with Mott insulators. These materials, according to band theory,* should be conductors but, in practice, are dielectrics (insulators). In general terms, the mechanism behind this anomaly is known to physicists, though a complete theory for Mott insulators does not yet exist. They do not fully understand how the materials transform from insulators into conductors.

* Band theory is a quantum theory developed in the first half of the 20th century to explain the electrical properties of substances. The theory is based on the idea of quantum energy states. Electrons in a substance either have both sufficient energy and free transition and, thus, are able to enter the zone of conductivity, or they do not, in which case it becomes what researchers call a "forbidden zone."

At the same time, preliminary estimates indicate that this effect is capable of opening a new path to faster computers. Motto transition occurs under the influence of several factors, including a magnetic field, which allows it to be controlled from outside. This makes it possible for researchers to permit current flow or to stop it at a necessary point. Such a scheme could replace common transistors and, in this case, allow them to be faster and more compact. But to do so, scientists must utilize the theory of Motto transition.

The theory belongs to fundamental conceptions explaining the electrical properties of a substance. It has a direct relation not only to Motto insulator behavior but also to superconductivity and the fundamentals of spintronics, a technology that could allow the control of electron spin.* Superconductivity and spintronics are among those trends where one can expect radical technological breakthrough, which is what makes understanding the nature of Motto transition so important - and not only from a purely theoretical point of view.

* Physicists define spin (spin up and spin down) as a quantum quantity, which "shows itself" when a particle interacts with a magnetic field. Spin plays a fundamental role in quantum physics because, without considering spin, it is impossible to describe the behavior of electrons in atoms, the phenomenon of material magnetization or molecular structure. The phenomenon of magnetic resistance goes together with spin. This can be seen when a sample is placed in a magnetic field and its electrical resistance dramatically changes; the effect is also seen in all modern hard drives.

In their new research, the physicists used a special model that allowed them to study quantum processes in the Motto insulator with the aid of so-called magnetic vortices. In this model, which was proposed by Valery Vinokur and David Nelson in 1993, electric current actuates a quantum vortex in a superconducting material, and one can consider such vortices to be the charge carrier. At this point - which is most significant, and about which Vinokur and Nelson wrote when discussing phase transitions* in their work - the superconductor with magnetic vortices behaved either like superfluid liquid or like glass, through which electric current cannot pass. By varying the temperature and the magnetic field, the scientists converted the sample from one state to another, and these observations together with the set of newer data were used as a basis for the new research.

* Phase transitions - transition of a substance from one state to another. A classic example is ice melting and turning into water, or water evaporating to become vapor. The demagnetization of a magnetized needle by heating it with a candle flame, which is an experiment that is also conducted in school, is another example of phase transition. Phase transitions are part of the study of thermodynamics, and they are connected with changes in the characteristics of a system such as total energy, entropy and order.

For the new experiment, the scientists created a quadrangular matrix on a silicon slab from 300?300 niobium "islets" with a diameter of about 220 nanometers and attached gold and niobium contacts to it. They made the sample using standard photolithograph methods, and then placed it in a cryostat, allowing it to cool to 1.4 kelvins, which is lower than the temperature needed for niobium to transition to a superconducting state. The niobium islets became superconductors, magnetic vortexes formed in them, and the researchers then analyzed the behavior of the system in different conditions.

Pic. The matrix made from niobium islets used in the experiments, its relief and cross-section, as well as a general view (C) in the optical microscope. Illustration courtesy of the researchers.

In particular, they measured the sample resistance and discovered that this quantity changes nonlinearly with an increasing magnetic field. From a theoretical point of view, the results suggest that one can view Motto transition as the transition of a substance from a liquid state to a gas, which opens up additional opportunities for analyzing the phenomenon from the perspective of thermodynamics. The experimental scheme developed by the scientists makes further experiments comparatively simple, because they have a sufficient amount of photolithograph methods and temperatures comparable with the temperature of liquid helium. It is worth noting that the low temperatures were achieved without the use of expensive liquid helium, and last year MIPT installed a similar unit in the laboratory at the Interdisciplinary Center for Basic Research.

Nonlinear resistance of the sample and the influence of magnetic fields upon electrical resistance. Illustration courtesy of the researchers.

###

The article has been published in the journal Science and is available at arxiv.org.

Link to the article: http://www.sciencemag.org/content/349/6253/1202

It is signed by researchers from Twente University (the Netherlands, second place of employment for Aleksandr Golubov), Rome International Center for Materials Science Center RICMASS, the Institute of Semiconductor Physics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk State University, Argonne National Laboratory (the USA), Queen Mary University of London, and MIPT.

Media Contact

Stanislav Goryachev
stas.goryachev@gmail.com
7-964-501-2307

 @phystech

http://mipt.ru/en/ 

Stanislav Goryachev | EurekAlert!

Further reports about: experiments insulators islets magnetic field phenomenon physics temperature vortices

More articles from Physics and Astronomy:

nachricht Unconventional superconductor may be used to create quantum computers of the future
19.02.2018 | Chalmers University of Technology

nachricht Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Contacting the molecular world through graphene nanoribbons

19.02.2018 | Materials Sciences

When Proteins Shake Hands

19.02.2018 | Materials Sciences

Cells communicate in a dynamic code

19.02.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>