Past Winner
2005 NSERC Howard Alper Postdoctoral Prize

Kyle Shen

Physics

The University of British Columbia

It's one of the great mysteries of 21st century physics: Why are some materials superconductors at relatively high temperatures? Unlock this secret and you may be a shoo-in for a Nobel Prize in physics. Even seeing pieces of this puzzle has garnered University of British Columbia postdoctoral fellow Dr. Kyle Shen international acclaim and NSERC's 2005 Howard Alper Postdoctoral Prize.

Just months into his new research digs in the UBC lab of renowned condensed matter physicist Professor George Sawatzky, Dr. Shen (who prefers to go by Kyle) is in the process of taking his research to a new level. For the Vancouverite, it's a homecoming after a 10-year scientific odyssey through undergraduate studies at the Massachusetts Institute of Technology and graduate school at Stanford that saw him emerge as a young researcher to watch – and listen to. Since completing his PhD at Stanford in the spring of 2005, Dr. Shen's been on a hectic international tour: he spent two months as a visiting scientist at the University of Tokyo, followed by invited talks at Oxford, Cornell and the Max Planck Institute in Germany.

It's attention that reflects the fact that Dr. Shen's area of research is hot. Relatively speaking. Superconductors are materials in which the electrons travel free of resistance. If your stove coil were a superconductor, you'd turn it on but it would never heat up because the electrons would whiz through it without resistance.

The absence of resistance means that superconductors could have huge potential for industry: they conduct electrical current without heat loss. A laptop computer with superconducting materials wouldn't generate heat. The challenge is that materials like lead and tin only become superconductors within a few degrees of absolute zero, or – 273°C, making them impractical for most commercial uses.

Enter the high-temperature superconductors (HTSCs). Discovered in 1987, these materials offer no resistance up to a comparatively balmy – 140°C. The big question is why?

Dr. Shen's doctoral research focused on studying a group of HTSCs that offer unique clues into the nature of HTSCs. These HTSCs are normally insulators – electrons don't flow through them at all at room temperature. But when a few atoms of other elements are added, these insulators perform a head-scratching physics 180° turn – they become HTSCs.

"If you use conventional thinking these materials shouldn't be superconductors, or even behave like metals. They should remain insulators," says Dr. Shen.

He says the challenge is to understand what it is about how the electrons are interacting with one another and ordered that gives rise to superconductivity. To do this, Dr. Shen and his lab colleagues at Stanford used a sophisticated technique, called photoemission spectroscopy, to painstakingly tease out nanoscale information about these electron interactions.

At the Stanford Radiation Laboratory they bombarded HTSC materials with intense beams of ultraviolet light. The ultraviolet rays literally kicked out electrons from their crystals of HTSC material. By measuring the trajectories of these ejected electrons, Shen's team was able to correlate the electrons' initial energy and momentum within the material, like following the trajectory of a soccer ball back to its kicker.

Their experiments confirmed that the electrons are ordered in a checkerboard pattern within the HTSC crystal. Most notably for their paper in Science, they discovered that the electrons moved and interacted very differently along the diagonals versus the edges of the checkerboard pattern.

It was an insight that called for 30-hour sleepless stretches as Dr. Shen tended his experiment.

"The most interesting results I've found only came after weeks or months of data analysis," says Dr. Shen.

Now he's preparing once again for long nights, this time at the new Canadian Light Source (CLS) synchrotron in Saskatoon where he'll continue to explore nanoscale electron ordering in materials. The research will mark a new era in Canadian condensed matter physics. The CLS is Canada 's first synchrotron. Along with enabling scientists to peer into the nature of matter, it's drawing these scientists to Canada in the first place. Dr. Sawatzky, a world-leading physicist, was recently attracted back to Canada with a Canada Research Chair and the directorship of UBC's new Advanced Materials and Process Engineering Laboratory after three decades in the Netherlands .

It's an ordering of events – the people, facilities and family – that for Dr. Shen can fuel an international science career at home.