20 November 2015

Magnetic field driven phase transition in underdoped YBCO

A phase diagram shows the large variety of phases that can exist at different values of magnetic field.

Just as all matter may exist in the three famous everyday phases — solid, liquid and gas — complex materials may exist in a combination of subtle phases not apparent to the eye. This finding shows that a class of materials, which all contain copper oxide and are known to exhibit a variety of subtle phases, may have even more complexity than thought. And, in fact, some phases are brought about not by changes in temperature but magnetic field.

What did scientists discover?

The electrons in many materials have a complex organization that can change in response to temperature, magnetic field or slight tweaks to its chemical composition. Such organization within a material is called a "phase." Researchers observed a transition between two phases in the most famous high-temperature superconductors (YBCO, or yttrium barium copper oxide) that was brought about by an intense magnetic field. The phases were discovered by specific heat, the measurement of the temperature increase of a material that occurs when it absorbs energy.

Why is this important?

Research to understand the high-temperature, copper-oxide superconductors has been going on for nearly three decades, with the ultimate answer remaining elusive. This finding shows just how complex these materials are: There is a transition between two phases that is driven by an intense magnetic field. One extremely odd feature of this phase transition is that both phases exhibit superconductivity, thus existing within an overarching “superconducting phase,” the phase of zero electrical resistance that characterizes high-temperature superconductors.

Who did the research?

J. B. Kemper1, O. Vafek2, J. B. Betts3, F. F. Balakirev3, W. N. Hardy4,5, Ruixing Liang4,5, D. A. Bonn4,5, and G. S. Boebinger2

1Washington State University; 2National High Magnetic Field Laboratory and Florida State University; 3Los Alamos National Laboratory; 4University of British Columbia; 5Canadian Institute for Advanced Research

Why did they need the MagLab?

THE TOOLS THEY USED

This research was conducted in the 35 tesla resistive magnet at the MagLab's DC Field Facility.

The MagLab has a unique capability to measure specific heat with extreme precision to 35 teslas, which was required to observe the phase transition and characterize the behavior of the two phases. The nature of this transition and the behavior of the high-magnetic-field phase remain mysterious. Understanding them might ultimately provide clues to the mechanism for high-temperature superconductivity.

Details for scientists

Funding

This research was funded by the following grants: Boebinger (NSF DMR-1157490), Lord (NSF CHE-1039925), Hardy, Liang and Bonn (Natural Science and Engineering Research Council of Canada and the Canadian Institute for Advanced Research)

For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it..

Details

  • Research Area: Condensed Matter Technique Development, Superconductivity - Basic
  • Research Initiatives: Materials
  • Facility / Program: DC Field
  • Year: 2015
Last modified on 20 November 2015
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