Taking our understanding of quantum matter to new levels, scientists at Los Alamos National Laboratory are exposing high-temperature superconductors to very high magnetic fields, changing the temperature at which the materials become perfectly conducting and revealing unique properties of these substances.

The eventual goal of the research would be to create a superconductor that operates at room temperature and needs no cooling at all. At this point, all devices that make use of superconductors, such as the MRI magnets found in hospitals, must be cooled to temperatures far below zero with liquid nitrogen or helium, adding to the cost and complexity of the enterprise.

High-temperature superconductors have been a thriving field of research for almost 30 years, not just because they can conduct electricity with no losses—one hundred degrees higher than any other material—but also because they represent a very difficult and interesting “correlated-electron” physics problem in their own right.

The Los Alamos team’s research in the 100-T magnet found that if one dopes YBa2Cu3O6+x to the point where Tc is highest (“optimal doping”), the electrons become very heavy and move around in a correlated way.

“This is a vital piece of information for building the next theory of superconductivity.”Brad Ramshaw, Los Alamos National Laboratory scientist.

“This tells us that the electrons are interacting very strongly when the material is an optimal superconductor,” said the researcher. “This is a vital piece of information for building the next theory of superconductivity.”

Proof of its existence has previously not been found due to the robust nature of the superconductivity in the copper oxide materials, yet if scientists can show that there is a quantum critical point, it would constitute a significant milestone toward resolving the superconducting pairing mechanism, Ramshaw explained.

“Assembling the pieces of this complex superconductivity puzzle is a daunting task that has involved scientists from around the world for decades,” said Charles H. Mielke, NHMFL-Pulsed Field Facility director at Los Alamos. “Though the puzzle is unfinished, this essential piece links unquestionable experimental results to fundamental condensed matter physics - a connection made possible by an exceptional team, strong partner support and unsurpassed capabilities.

Strong magnetic fields such as the world-record field accessible at the NHMFL site at Los Alamos enable the normal metallic state to be accessed by suppressing superconductivity. Fields approaching 100 tesla, in particular, enable quantum oscillations to be measured very close to the maximum in the transition temperature Tc ~ 94 kelvin. These quantum oscillations give scientists a picture of how the electrons are interacting with each other before they become superconducting.

By accessing a very broad range of dopings, the authors show that there is a strong enhancement of the effective mass at optimal doping. A strong enhancement of the effective mass is the signature of increasing electron interaction strength, and the signature of a quantum critical point. The broken symmetry responsible for this point has yet to be pinned down, although a connection with charge ordering appears to be likely, Ramshaw notes.

This story is reprinted from material from Los Alamos National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.