University of Minnesota
School of Physics & Astronomy

Spotlight

Link between charge order and quantum oscillations found in high temperature superconductors

Martin Greven
Martin Greven
Richard Anderson
                                                       

Professor Martin Greven of the School of Physics and Astronomy has led a research effort that found a link between quantum oscillations and charge order in high temperature superconductors. Superconductivity is a quantum mechanical phenomenon of exactly zero electrical resistance and expulsion of magnetic fields that occurs in certain materials when cooled below a characteristic critical temperature.

Greven states that: “The phenomenon of superconductivity at temperatures higher than that of liquid nitrogen (77 K or - 320 Fahrenheit) has been one of the hottest research areas in physics during the past three decades. Our work points to a universal connection between two seemingly distinct phenomena: quantum oscillations, exhibited by the electrical resistivity once superconductivity is destroyed by a large magnetic field, and charge order, which competes with superconductivity in the absence of a magnetic field.”

Greven says this is part of a larger effort by the group to understand the exotic physics of high temperature superconductors. There exist hundreds of known high-temperature superconductors, which are promising materials in terms of providing society with hoped-for applications such as fast magnetically levitated trains and efficient energy storage. The particular material samples that were studied, high-quality crystals of Hg-Ba-Cu-O, were created in the research group’s laboratory in the new Physics and Nanotechnology building. Hg-Ba-Cu-O crystals are ideal for experimental study because they have a relatively simple crystalline structure and are superconducting up to temperatures of nearly 100 K (- 280 Fahrenheit).

The group subjected the samples to very intense X-ray beams at several major laboratories, including the Advanced Photon Source at Argonne National Laboratory in Illinois. From the way the X-rays are scattered off the crystals, it is possible to learn about subtle ordering phenomena that involve the crystal’s charged electrons. Once the electrons slow down and form ordered structures, they are no longer able to participate in the superconductivity.

Greven says that the charge order in the Hg-Ba-Cu-O crystals was surprisingly weak. He anticipates that materials that superconduct at even higher temperatures may exhibit no charge order at all. “Our lab at the University of Minnesota is in the unique position to grow good and large crystals of these most desirable materials. In the coming years, we hope to build on this success and to further improve our knowledge of the interconnection between charge order and charge transport.”

Martin Greven is Principal Investigator for an international collaboration which includes scientists from AGH-University of Science in Poland, Peking University in China, Max Planck Institute for Solid State Research in Germany, The Polytechnic University of Milan, Iowa State University, the Helmholz Center Berlin and the Paul Scherrer Institute in Switzerland. The work in the U.S. received funding from the Department of Energy’s Office of Basic Energy Services. It was published in the journal Nature Communications.10.1038/ncomms6875).