The quest for a material which could conduct electricity excluding the resistance of room temperature has motivated scientists in Germany and they have identified a common molecule hydrogen sulphide superconducting at a record breaking 203 kelvin when the same is exposed to very high pressure.
The outcome approves initial observations which were released by the researchers late last year. It has alsobeen verified from data collected from various other groups though some of the physicist had asked to be cautious. According to Ivan Schuller from the University of California in San Diego, he states that `the results seems to be promising but are not yet watertight.
However, Antonio Bianconi, director of the Rome International Centre for Materials Science Superstripes – RICMASS, is of the opinion that the evidence is compelling. He has described the finding as – main breakthrough, in quest for a room temperature superconductor since the discovery of 1986 superconductivity in cuprates, exotic ceramic compounds which display the phenomenon up to 164 K. Mikhail Eremets together with two other physicists at the Max Planck Institute for Chemistry in Mainz reported last December, that they had found hydrogen sulfide superconducting below 190 K.
The Meissner Effect
When the same was placed a 10 micrometre-wide sample of the material in a diamond anvil cell, subjected to a pressure of around 1.5 million atmospheres, it was found that its electrical resistance reduced more than a factor of 1,000 when it cooled below the threshold or critical temperature. However, at that point of time, the researchers were unable to demonstrate a second key characteristic of superconductivity which is known as Meissner effect, wherein samples tend to excel a magnetic field when the same is cooled below the critical temperature.
The authors in their latest work had got together along with two physicists from the University of Mainz for the purpose of building a non-magnetic cell to acquire a very sensitive form of magnetometer known as SQUID. They had placed 50 micrometre wide samples of hydrogen sulphide under pressure of up to 2 million atmospheres in an external magnetic field, gradually warming them, beginning from a few degrees above zero. They investigated the sign of the Meissner effect, a sudden increase in the magnetization signal of the sample, when the temperature had increased beyond 203 K.
Researchers Cynical on Results
The researchers measured a higher critical temperature than they did last year, to observe tiny variation in the samples’ crystal structure. Bianconi has stated that several superconductivity researchers were cynical on the results when in March, at the conference of the American Physical Society in San Antonio, Texas, they were presented.
A physicist at Osaka University in Japan, Katsuya Shimizu stated that he together with his colleagues had confirmed the 190 K electrical transition, utilising their own refrigerator in holding many samples and cells that were provided by Eremets. Sculler debates that the Mainz group could do some more investigations to ensure that they have not overlooked an uncontrolled artefact like the background noise selected during the subtle measurement of magnetization.
