Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A new look at high-temperature superconductors

26.02.2013
Method allows direct detection of rapid fluctuations that may help to explain how high-temperature superconducting materials work.

While the phenomenon of superconductivity — in which some materials lose all resistance to electric currents at extremely low temperatures — has been known for more than a century, the temperature at which it occurs has remained too low for any practical applications.

The discovery of “high-temperature” superconductors in the 1980s — materials that could lose resistance at temperatures of up to negative 140 degrees Celsius — led to speculation that a surge of new discoveries might quickly lead to room-temperature superconductors. Despite intense research, these materials have remained poorly understood.

There is still no agreement on a single theory to account for high-temperature superconductivity. Recently, however, researchers at MIT and elsewhere have found a new way to study fluctuating charge-density waves, which are the basis for one of the leading theories. The researchers say this could open the door to a better understanding of high-temperature superconductivity, and perhaps prompt new discoveries of higher-temperature superconductors.

The findings were published this week in the journal Nature Materials by assistant professor of physics Nuh Gedik; graduate student Fahad Mahmood; Darius Torchinsky, a former MIT postdoc who is now at the California Institute of Technology; and two researchers at Brookhaven National Laboratory.

Explaining the basis for high-temperature superconductivity remains “the hardest problem in condensed-matter physics,” Gedik says. But one way of getting a handle on this exotic state of matter is to study what happens to these materials near their “transition temperature,” the point below which they become superconductors.

Previous experiments have shown that above the transition temperature, there is a peculiar state where, Gedik says, “the material starts to behave very weirdly”: Its electrons act in unusual ways, which some physicists believe is caused by a phenomenon called charge-density waves. While the electron density in most conductors is uniform, Gedik explains, in materials with charge-density waves the density is distributed in a sinusoidal pattern, somewhat like ripples on a pond. But so far, such charge-density waves have only been detected in high-temperature superconductors under special circumstances, such as a particular level of doping (the introduction of atoms of another element onto its surface).

Some researchers have proposed that these waves are elusive in high-temperature superconductors because they fluctuate very rapidly, at speeds measured in picoseconds (trillionths of a second). “You can’t see it with conventional techniques,” Gedik says.

That’s where Gedik’s new approach comes in: His team has spent years perfecting methods for studying the movement of electrons by zapping them with laser pulses lasting just a few femtoseconds (or quadrillionths of a second), and then detecting the results with a separate laser beam.

Using that method, the researchers have now detected these fluctuating waves. To do this, they have selectively generated and observed two different collective motions of electrons in these waves: variation in amplitude (the magnitude of modulation of the waves) and in phase (the position of the troughs and peaks of the waves). These measurements show that charge density waves are fluctuating at an interval of only about 2 picoseconds.

“It’s not surprising that static techniques didn’t see them,” Gedik says, but “this settles the question: The fluctuating charge-density waves do exist” — at least in one of the cuprate compounds, the first high-temperature superconducting materials discovered in the 1980s.

Another question: What role, if any, do these charge-density waves play in superconductivity? “Are they helping, or are they interfering?” Gedik asks. To answer this question, the researchers studied the same material, with optimal doping, in which the superconducting transition temperature is maximized. “We see no evidence of charge-density waves in this sample,” Gedik says. This suggests that charge-density waves are probably competing with superconductivity.

In addition, it remains to be seen whether the same phenomenon will be observed in other high-temperature superconducting materials. The new technique should make it possible to find out.

In any case, detecting these fluctuations could help in understanding high-temperature superconductors, Gedik says — which, in turn, could “help in finding other [superconducting materials] that actually work at room temperature.” That elusive goal could enable significant new applications, such as electric transmission lines that eliminate the losses that now waste as much as 30 percent of all electricity produced.

David Hsieh, an assistant professor of physics at Caltech, says the phenomena detected by this research “are known to be very difficult to detect,” so this work “is a great technical achievement and a high-quality piece of research.” By showing for the first time that the fluctuating charge-density waves seem to compete with superconductivity, he says, “It provides the insight that finding a way to suppress this fluctuating charge-density wave order may simultaneously increase” the temperature limits of superconductivity.

The work, which also included researchers Anthony Bollinger and Ivan Bozovic of Brookhaven National Laboratory, was supported by grants from the National Science Foundation and the U.S. Department of Energy.

Sarah McDonnell | EurekAlert!
Further information:
http://www.mit.edu

More articles from Materials Sciences:

nachricht New value added to the ICSD (Inorganic Crystal Structure Database)
27.03.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

nachricht Argon is not the 'dope' for metallic hydrogen
24.03.2017 | Carnegie Institution for Science

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>