Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Superconductivity: No resistance at record temperatures

18.08.2015

Hydrogen sulfide loses its electrical resistance under high pressure at minus 70 degrees Celsius

For many solid-state physicists, superconductors that are suitable for use at room temperature are still a dream. Up until now, the only materials known to conduct current with no electrical resistance and thus no loss did so only at very low temperatures.


The apparatus to generate high pressures, is amazingly handy. The researchers press the metal cell with screws together. The high pressure created in the center of the cell, only diamonds resist.

Thomas Hartmann

Accordingly, special copper ceramics (cuprates) took the leading positions in terms of transition temperature—the temperature at which the material loses its resistance. The record for a ceramic of this type is roughly minus 140 degrees Celsius at normal air pressure and minus 109 degrees Celsius at high pressure. In the ceramics, a special, unconventional form of superconductivity occurs. For conventional superconductivity, temperatures of at least minus 234 degrees Celsius have so far been necessary.

A team led by Mikhael Eremets, head of a working group at the Max Planck Institute for Chemistry, working in collaboration with the researchers at Johannes Gutenberg University Mainz has now observed conventional superconductivity at minus 70 degrees Celsius, in hydrogen sulfide (H2S).

To convert the substance, which is a gas under normal conditions, into a superconductor the scientists did however have to subject it to a pressure of 1.5 megabar (1.5 million bar), as they describe in the latest edition of the science magazine Nature.

The transition temperature of conventional superconductivity knows no limits

“With our experiments we have set a new record for the temperature at which a material becomes superconductive,” says Mikhael Eremets. His team have also been the first to prove in an experiment that there are conventional superconductors with a high transition temperature. Theoretical calculations had already predicted this for certain substances including H2S.

“There is a lot of potential in looking for other materials in which conventional superconductivity occurs at high temperatures,” says the physicist. “There is theoretically no limit for the transition temperature of conventional superconductors, and our experiments give reason to hope that superconductivity can even occur at room temperature.”

The researchers generated the extremely high pressure required to make H2S superconductive at comparatively moderate negative temperatures in a special pressure chamber smaller than one cubic centimeter in size. The two diamond tips on the side, which act as anvils, are able to constantly increase the pressure that the sample is subjected to. The cell is equipped with contacts to measure the electrical resistance of the sample. In another high-pressure cell, the researchers were able to investigate the magnetic properties of a material that also change at the transition temperature.

After the researchers had filled the pressure chamber with liquid hydrogen sulfide, they increased the pressure acting on the sample gradually up to roughly two megabar and changing the temperature for each pressure level. They took measurements of both resistance and magnetization to determine the material’s transition temperature. The magnetization measurements provide very useful information, because a superconductor possesses ideal magnetic properties.

Hydrogen atoms facilitate superconductivity at high temperatures

The researchers believe that it is mainly hydrogen atoms that are responsible for hydrogen sulfide losing its electrical resistance under high pressure at relatively high temperatures: Hydrogen atoms oscillate in the lattice with the highest frequency of all elements, because hydrogen is the lightest.

As the oscillations of the lattice determine the conventional superconductivity—and do this more effectively the faster the atoms oscillate—materials with high hydrogen content exhibit a relatively high transition temperature. In addition, strong bonds between the atoms increase the temperature at which a material becomes superconductive. These conditions are met in H3S, and it is precisely this compound that develops from H2S at high pressure.

Mikhael Eremets and his team are now looking for materials with even higher transition temperatures. Increasing the pressure acting on the hydrogen sulfide above 1.5 megabar is not helpful in this case. This has not only been calculated by theoretical physicists, but now also confirmed in experiments performed by the team in Mainz. At even higher temperatures the electron structure changes in such a way that the transition temperature slowly begins to drop again.

Wanted: hydrogen-rich materials with a higher transition temperature

“An obvious candidate for a high transition temperature is pure hydrogen,” says Mikhael Eremets. “It is expected that it would become superconductive at room temperature under high pressure.” His team has already begun experimenting with pure hydrogen, but the experiments are very difficult as pressures of three to four megabar are required.

“Our research into hydrogen sulfide has however shown that many hydrogen-rich materials can have a high transition temperature,” says Eremets. It may even be possible to realize a high-temperature superconductor worth the name in terms of common temperature perception without high pressure. The researchers in Mainz currently need the high pressure to convert materials that act electrically insulating like hydrogen sulfide into metals.

“There may be polymers or other hydrogen-rich compounds that can be converted to metals in some other way and become superconductive at room temperature,” says the physicist. If such materials can be found, we would finally have them: superconductors that can be used for a wide range of technical applications. SB/PH

Original publication:
Conventional superconductivity at 203 K at high pressures
Alexander Drozdov, Mikhail Eremets, Ivan Troyan, Vadim Ksenofontov, Sergii Shylin Nature, 17. August 2015

Weitere Informationen:

http://www.mpic.de/en/news/press-information/news/supraleitung-widerstandslos-be...

Dr. Susanne Benner | Max-Planck-Institut für Chemie

More articles from Life Sciences:

nachricht Separating methane and CO2 will become more efficient
18.10.2017 | KU Leuven

nachricht Bolstering fat cells offers potential new leukemia treatment
17.10.2017 | McMaster University

All articles from Life Sciences >>>

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

Researchers release the brakes on the immune system

18.10.2017 | Health and Medicine

Separating methane and CO2 will become more efficient

18.10.2017 | Life Sciences

Ocean atmosphere rife with microbes

17.10.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>