16 Jan 2015

Charge ordering phenomenon discovered in electron-doped high-temperature superconductors

SASKATOON – Using the Canadian Light Source synchrotron, physicists have detected charge ordering for the first time in electron-doped copper-oxide (cuprate) superconductors, as reported today in Science. The discovery comes as a great surprise, as past research created the expectation that charge ordering should only occur when researchers use hole-doping to obtain superconductivity in the cuprates.

The resonant X-ray scattering study, performed at the REIXS beamline at CLS, was headed by University of British Columbia postdoctoral fellow and Global Scholar with the Canadian Institute for Advanced Research, Eduardo H. da Silva Neto, and PhD student Riccardo Comin (now a postdoc fellow at the University of Toronto). These new results represent another milestone in the long standing collaboration between the REIXS beamline, managed and operated by CLS scientists Feizhou He and Ronny Sutarto, and professors George Sawatzky and Andrea Damascelli from the UBC’s Quantum Matter Institute and the Max Planck-UBC Centre for Quantum Materials.

Superconductivity is a phenomenon by which electrical currents can flow through a material with zero electrical resistance, a feature that is already exploited in electromagnets used in MRI machines, and has great potential in applications such as power transmission. However, even the so-called high-temperature superconductors still require cryogenic temperatures far below room temperature.

In cuprates, superconductivity can be achieved by either adding or removing electrons from the parent compound. It has been known for a few years now that in compounds undergoing the later process, called hole-doping, a phenomenon by the name of charge order competes with superconductivity.

“The challenge now is to understand what the mechanism of charge order is. If we can weaken it, we might then be able to achieve superconductivity closer to room-temperature,” da Silva Neto said.

So far past research has indicated that charge ordering was restricted to hole-doped cuprates and that it required hole-doped-specific phenomena to occur. The present study reveals that charge ordering can also occur in electron-doped cuprates, and provides a new avenue to study charge ordering and its relationship to superconductivity in these materials.

“Now we can compare and contrast characteristics that are common across both flavors of copper-oxide materials,” said UBC Professor Andrea Damascelli, leader of the research team.

The researcher’s new findings show that charge ordering is universal phenomenon to both electron- and hole-doped materials and in future works, understanding its microscopic origin in relation to superconductivity will bring us one step closer to the ultimate goal, i.e., an energy-efficient superconducting material.

CLS Research Associate Ronny Sutarto (l-r), UBC physicist Eduardo de Silva Neto and Feizhou He, REIXS Beamline Scientist
Cite: da Silva Neto, Eduardo H., et al. "Charge ordering in the electron-doped superconductor Nd2-xCexCuO4." Science Vol. 347, no. 6219, pp. 282 (2015). 
DOI: 10.1126/science.1256441
This photo and others to accompany this story are available in the CLS image gallery for use with a Creative Commons licence.

About the CLS:

The Canadian Light Source is Canada’s national centre for synchrotron research and a global centre of excellence in synchrotron science and its applications. Located on the University of Saskatchewan campus in Saskatoon hosted over 2,000 researchers from academic institutions, government, and industry from 10 provinces and 2 territories; delivered over 32,000 experimental shifts; received over 8,300 user visits; and provided a scientific service critical in over 1,000 scientific publications, since beginning operations in 2005. The CLS has over 200 full-time employees.

CLS operations are funded by Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, Western Economic Diversification Canada, National Research Council of Canada, Canadian Institutes of Health Research, the Government of Saskatchewan and the University of Saskatchewan.

Synchrotrons work by accelerating electrons in a tube to nearly the speed of light using powerful magnets and radio frequency waves. By manipulating the electrons, scientists can select different forms of very bright light using a spectrum of X-ray, infrared, and ultraviolet light to conduct experiments.

Synchrotrons are used to probe the structure of matter and analyze a host of physical, chemical, geological and biological processes. Information obtained by scientists can be used to help design new drugs, examine the structure of surfaces in order to develop more effective motor oils, build more powerful computer chips, develop new materials for safer medical implants, and help clean up mining wastes, to name a few applications.

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