The search for new superconducting materials has waxed and waned over the past couple of decades as researchers have struggled to find the right mix for nurturing this remarkable phenomenon at temperatures much higher than absolute zero. This work now centres on analyzing the microscopic changes taking place within a superconductor when it hits that key temperature where mobile electrons organize into a wave-like periodic structure called a charge density wave.

The theoretical models for this behaviour describes charges lining up in either parallel lines or a well-ordered checkerboard pattern but until now it has been impossible to discern one from the other at the experimental level. That limitation has been overcome through work led by Riccardo Comin, a graduate of the University of British Columbia in the group of Andrea Damascelli and now an NSERC post-doctoral fellow with Ted Sargent at the University of Toronto. Comin assembled a two-dimensional picture of electronic density waves within a sample by combining successive one-dimensional scans by a synchrotron. 

The result was published earlier this year in Science, where Comin and his colleagues suggest that this perspective on charge density waves could breathe new life into the field of high temperature superconductors. He recalls witnessing the potential of this technique for himself as he was finishing his doctoral studies in 2013. “We decided to take a look at the other compounds that had not yet been studied this way, where people had not yet found these kinds of effects,” Comin says, pointing to a number of cuprates, the copper and oxygen compounds that have been among the leading contenders for high-temperature superconductivity.

After subjecting samples to repeated synchrotron scans in much the same way that medical tomography builds a complete picture from individual slices, electrons within these cuprates revealed an arrangement of electrons resembling stripe-like structures. While questions persist around just how this pattern emerges, Comin insists that this confirmation should facilitate progress toward honing superconducting materials that function ever closer to room temperature. “Our greatest contribution was to envision new variations and extensions on a basic experimental scheme that were fortunately successful in revealing the structure of this ordered space.”