23 January 2020

Nematic Phase Weakens Superconductivity

(a) The phase diagram of FeSe0.89S0.11 which shows two distinct superconducting domes that are separated by a change of the Fermi surface at intermediate pressures (i.e. Lifshitz transition). (c) This is confirmed by a shift in the quantum oscillation frequencies with higher pressures. The largest oscillations shown (blue) are for a temperature of 0.3K. (a) The phase diagram of FeSe0.89S0.11 which shows two distinct superconducting domes that are separated by a change of the Fermi surface at intermediate pressures (i.e. Lifshitz transition). (c) This is confirmed by a shift in the quantum oscillation frequencies with higher pressures. The largest oscillations shown (blue) are for a temperature of 0.3K. Pascal Reiss, Amalia Coldea, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK

A nematic phase is where the molecular/atomic dynamics show elements of both liquids and solids, like in liquid crystal displays on digital watches or calculators. Using high magnetic fields and high pressure, researchers probed the electronic states of an iron-based superconductor and found that its nematic state weakened superconductivity.

THE TOOLS THEY USED

This research was conducted in the 45T hybrid magnet at the DC Field Facility.

What did scientists discover?

MagLab users studied the degree of electron interactions in FeSe0.89S0.11, a high-temperature superconductor that also exhibits a nematic state. What is unique in this material is that the nematic state has profound consequences for our understanding of high-temperature superconductivity. In the vicinity of the destruction of the nematic state in response to 5kbar of applied pressure, the electrons change from strongly influencing each other in the nematic phase to being more strongly influenced by the crystal lattice. As a result of the nematic phase, this material exhibits two distinct superconducting phases.

Why is this important?

These observations suggest that the nematic state actually weakens superconductivity and, for FeSe0.89S0.11 to achieve high-temperature superconductivity, another ingredient is needed such as magnetism.

Who did the research?

Pascal Reiss1, David Graf2, Amir A. Haghighirad1,3 and Amalia I. Coldea1

1University of Oxford; 2National MagLab at Florida State University; 3Karlsruhe Institute of Technology;

Why did they need the MagLab?

The experimental challenge was to access the normal state of superconductors above 20T, to detect quantum oscillations and determine the degree of electron interactions in very clean single crystals. These experiments required very high magnetic fields up to 45T at temperatures as low as 0.3K, coupled with pressure cells to tune the applied pressure from 0 to 20kbar (0 to 20,000 atmospheres), allowing access to many different electronic phases.

Details for scientists

Funding

This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490, NSF DMR-1644779); A.I. Coldea (EPSRC-UK: EP/I004475/1, EP/I017836/1; EP/M020517/1);


For more information, contact Tim Murphy.

Details

  • Research Area: Superconductivity - Basic
  • Research Initiatives: Materials
  • Facility / Program: DC Field
  • Year: 2020
Last modified on 24 January 2020