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 Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology

nachricht NASA team finds noxious ice cloud on saturn's moon titan
19.10.2017 | 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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>