ANOTHER TWIST IN THE FIELD OF SUPERCONDUCTIVITY

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ANOTHER TWIST IN THE FIELD OF SUPERCONDUCTIVITY
13 May 2007 - DOE/Brookhaven National Laboratory

Researchers at the U.S. Department of Energy’s Brookhaven National Laboratory have discovered an interesting type of electronic behavior in a recently discovered class of superconductors known as cobalt oxides, or cobaltates. These materials operate quite differently from other oxide superconductors, namely the copper oxides (or cuprates), which are commonly referred to as high-temperature superconductors.

When traditional superconductors are cooled to nearly absolute zero (0 Kelvin or –452 degrees Fahrenheit), pairs of negatively charged electrons exchange packets of vibrational energy known as phonons. This mechanism overcomes the repulsion of the like-charged particles and allows them to move together to carry electrical current with virtually no resistance. But the mechanism for superconductivity in the high-temperature cuprates, which act as superconductors at temperatures as “warm” as 138 K, is still one of the “hottest” mysteries in condensed matter physics. Above the superconducting transition temperature the cuprates do not exhibit normal electronlike behavior, so it’s unclear either how or what is pairing to carry the current.

With the discovery of a new class of oxide superconductors, the cobaltates (which become superconducting at a temperature around 5 K), scientists were naturally curious whether they could learn something about their mechanism to shed light upon this problem. “What we’ve found,” says Brookhaven physicist Peter Johnson, “has opened up another twist.”

As Johnson’s group cooled the cobalt-oxide materials, they observed electronlike excitations at temperatures well above the so-called transition temperature where the materials become superconductors. “If we had discovered these before we discovered the cuprates we’d probably think the same electron pairing mechanism was responsible for all superconductivity,” Johnson says.

http://www.bnl.gov

About: DOE/Brookhaven National Laboratory
Established in 1947 on Long Island, Upton, New York, Brookhaven is a multi-program national laboratory operated by Brookhaven Science Associates for the US Department of Energy (DOE). Six Nobel Prizes have been awarded for discoveries made at the Lab.

Brookhaven has a staff of approximately 3,000 scientists, engineers, technicians and support staff and over 4,000 guest researchers annually.

Brookhaven National Laboratory's role for the DOE is to produce excellent science and advanced technology with the cooperation, support, and appropriate involvement of our scientific and local communities. The fundamental elements of the Laboratory's role in support of the four DOE strategic missions are the following:

To conceive, design, construct, and operate complex, leading edge, user-oriented facilities in response to the needs of the DOE and the international community of users.

To carry out basic and applied research in long-term, high-risk programs at the frontier of science.

To develop advanced technologies that address national needs and to transfer them to other organizations and to the commercial sector.

To disseminate technical knowledge, to educate new generations of scientists and engineers, to maintain technical capabilities in the nation's workforce, and to encourage scientific awareness in the general public.

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