Less is more: Disorder raises the critical temperature of a cuprate superconductor

Elke Arenholz, CHESS

"Developing materials that exhibit superconductivity at room temperature for wide spread commercial use would allow a significant reduction in energy consumption throughout the power grid."

spin stripes

Right: In an ideal system, orthogonal charge-spin stripes in adjacent layers prevent Josephson coupling between layers. Left: In the presence of disorder, distorted stripes around defects are not orthogonal, which reestablishes Josephson coupling between layers and increases TC.

What did the Scientists Discover?
The origin of high-temperature superconductivity remains poorly understood to date. Over the past two decades, spatial oscillations of the electronic density known as charge-density waves (CDWs) have been found to coexist with high-temperature superconductivity in most prominent cuprate superconductors. The debate on whether CDWs help or hinder high-temperature superconductivity in cuprates is still ongoing. In principle, disorder at the atomic scale should strongly suppress both high-temperature superconductivity and CDWs. In this work, however, we find that disorder created by irradiation increases the superconducting critical temperature by 50% while suppressing the CDW order, showing that CDWs strongly hinder bulk superconductivity. We show that this increase occurs because the CDWs could be frustrating the superconducting coupling between atomic planes.

Broader Impacts of this work?
When a superconducting material is cooled below its critical temperature it shows exactly zero electrical resistance, i.e. electric current can move through the material without any losses or heating. Developing materials that exhibit superconductivity at room temperature for wide spread commercial use would allow a significant reduction in energy consumption throughout the power grid. While this is a dream today, fundamental research as presented here advances our understanding of the physics underlying superconductivity and helps pave the way for important new materials in the future.

Why is this important?
We observed an unexpected and large increase of the superconducting transition temperature, TC, in La1.875Ba0.125CuO4 after proton irradiation of pristine single crystals which reduces the structural order in the materials and induces defects. This increase in TC is in contrast to the behavior expected for the material and accompanied by a suppression of the CDW, thus evidencing the strong competition between CDW and bulk superconductivity in La1.875Ba0.125CuO4.

Why did this research need CHESS?
Charge-density waves (CDWs) are real-space periodic oscillations of the crystal electronic density accompanied by a lattice distortion. In order to provide uniform proton irradiation throughout the bulk, the LBCO crystals needed to be extremely small - typically less than 75 microns thick. The small, bright undulator beams of CHESS are ideal to measure weak CDW signals from such tiny microcrystals.

Collaborators:

  • Maxime Leroux, Materials Science Division, Argonne National Laboratory
  • Vivek Mishra, Materials Science Division, Argonne National Laboratory
  • Jacob P. C. Ruff, Cornell High Energy Synchrotron Source, Cornell University
  • Helmut Claus, Materials Science Division, Argonne National Laboratory
  • Matthew P. Smylie, Materials Science Division, Argonne National Laboratory
  • Christine Opagiste, Institut Néel, CNRS, Université Grenoble Alpes
  • Pierre Rodière, Institut Néel, CNRS, Université Grenoble Alpes
  • Asghar Kayani, Department of Physics, Western Michigan University
  • G. D. Gu, Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory
  • John M. Tranquada, Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory
  • Wai-Kwong Kwok, Materials Science Division, Argonne National Laboratory
  • Zahirul Islam, Advanced Photon Source, Argonne National Laboratory
  • Ulrich Welp, Materials Science Division, Argonne National Laboratory

Publication Citation:
M. Leroux et al., “Disorder raises the critical temperature of a cuprate superconductor,” Proc Natl Acad Sci USA, vol. 116, no. 22, p. 10691, May 2019. https://doi.org/10.1073/pnas.1817134116

How was the work funded?
High-energy transmission X-ray data were collected on beamline A2 at CHESS, which is supported by the National Science Foundation (NSF) under NSF Award DMR-1332208. The research at Argonne National Laboratory was supported by the US Department of Energy (DOE), Office of Science, Materials Sciences and Engineering Division as well as Office of Basic Energy Sciences. The work at Brookhaven National Laboratory was supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract DE-SC0012704.