The scientists are collectively recognized for their groundbreaking work in the field of high-temperature superconductivity. Through experiments conducted at IBM's T. J. Watson Research Center and the University of Illinois the four physicists resolved a long-standing question regarding the nature of the electron pairs that carry the supercurrent in high-temperature superconductors.
"The recognition of these outstanding scientists affirms IBM's commitment to long-term research in science and technology," said Paul Horn, senior vice president, IBM Research. "Their results have had a profound impact on our understanding of high-temperature superconductivity."
The Buckley Prize was established by AT&T Bell Laboratories in 1952 to annually recognize and encourage outstanding theoretical or experimental contributions to condensed matter physics. Only 54 other scientists have received the award, eleven of which have gone on to receive the Nobel Prize. The most recent IBM recipient, Rolf Landauer, was honored in 1995 for pioneering a new view of transport theory that has become fundamental to modern understanding of quantum coherent transport in metals. Other scientists who have been honored with the Buckley Award for their work at IBM include: Dean E. Eastman (1980), Frank F. Fang (1988), Alan B. Fowler (1988), Phillip J. Stiles (1988) and Richard Webb (1992).
Resolving the Debate
Drs. Kirtley and Tsuei's research resolved a problem that had split the condensed matter physics community since the discovery of high-temperature superconductivity in 1986. In high-temperature superconductors, electrons flow through materials at temperatures of up to 135 degrees Kelvin with no resistance. Although it was known that the pairing of electrons makes this flow possible, the mechanism that causes the pairing had been a mystery.
With their groundbreaking research, the IBM scientists discovered that the electron pairs have a d-wave pairing function. This finding represents a major step towards understanding the pairing mechanism, and may lead to the development of new materials that will conduct without resistance at even higher temperatures.
To investigate the symmetry of the superconducting pairs, Tsuei designed an experiment that uses a unique tri-crystal arrangement for orientating the pair wavefunction so that d- and s-wave pairing can be distinguished. By controlling the angle at which the boundaries of the crystals meet, Kirtley and Tsuei, using a scanning SQUID (Superconducting Quantum Interference Device) microscope, were able to observe a spontaneous circulating supercurrent at the junction of the three grain boundaries. Furthermore, they proved that the magnitude of the observed supercurrent corresponds to exactly half of the standard magnetic flux quantum. The direct observation of the spontaneously generated half-integer flux quantum effect in the tri-crystal experiments represents compelling evidence for d-wave pairing symmetry in high-temperature superconductors.
With the Buckley Prize, the American Physical Society recognizes Tsuei and Kirtley "for using phase-sensitive experiments in the elucidation of the orbital symmetry of the pairing functions in High-Tc superconductors."
Tsuei is a scientist in the Physical Sciences department at IBM's T.J. Watson Research Center, where he has worked since 1973. His early research focused on the electrical and magnetic properties of glassy metals, including amorphous superconductors and ferromagnets. His current research interests include pairing symmetry and the basic mechanism responsible for high-temperature superconductivity in copper oxides. Tsuei holds both his M.S. and Ph.D. degrees in Materials Science from the California Institute of Technology. He received his B.S. degree from the National Taiwan University. He was awarded a Max Planck Research Prize from Germany in 1992, and elected as an academician to the Academia Sinica in 1996.
Kirtley is also a scientist in the Physical Sciences department at IBM's T.J. Watson Research Center, which he joined in 1978. He has worked in a number of areas in condensed matter physics, including inelastic electron tunneling spectroscopy, non-equilibrium superconductivity, surface enhanced Raman scattering, electron heating in silicon dioxide, and low-temperature scanning tunneling microscopy. Since 1993 he has been involved in research using scanning SQUID microscopes. His recent work has focused on the tri-crystal experiment and high-temperature superconductors. Kirtley holds a M.S. and a Ph.D. in physics from the University of California at Santa Barbara, and did post-doctoral research at the University of Pennsylvania.
IBM Research is staffed by about 2,800 researchers working at laboratories in the United States, Switzerland, Japan, Israel and China. Major areas of research include computer systems, applications and solutions, systems technology, physical sciences, mathematical sciences, storage and communications. Further information about the technological achievements of IBM Research can be found at: http://www.research.ibm.com
For more information on Dr. Kirtley and Dr. Tsuei's research, please go to: http://www.research.ibm.com/sup/