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DOE Pulse
  • Number 446  |
  • August 24, 2015

More is different

Jigang Wang

Jigang Wang

“If there’s a theme to my research, it’s small things and complex things,” says Jigang Wang, a physicist at DOE's Ames Laboratory.

Wang’s fascination with the small started as an undergraduate physics student.

“I was interested in the scientific philosophy of reductionism: that to understand phenomena, we have to go to the small, smaller and smallest until we find and understand the most fundamental particles. That by understanding one small piece, we can better understand the whole,” says Wang.

The interest led him to study very small semiconductor nanostructures in graduate school and carbon nanotubes as a postdoctoral researcher. But, along the way, Wang turned to physicist Philip Warren Anderson’s concept of “more is different,” which emphasizes the importance of complexity – how small particles organize themselves and how the organization creates different levels of principles that help explain the whole.

“We see that this concept cuts across different subdisciplines of physics, biology, chemistry, and applied science, and, of course, also in materials science, like superconductivity or magnetism,” says Wang. “You have these fascinating functions from these many particles bound by simple interactions. I study these complex systems: their dynamics, or how they change; how certain changes in the systems correlate to other changes to drive cooperative behaviors; and their nonlinearity, or how the output from a system is different from the input, to build functionalities.”

“More is indeed different,” he adds. “And my goal using femto-second laser spectroscopy is to build our understanding how these complex quantum materials work by revealing their organization principles from nanoscale to mesoscale and how we can harness their properties for energy applications.”

Wang uses femto-second laser spectroscopy to “see” tiny actions in real time in materials.  He and his research team apply a pulse laser to a sample to excite the material. Some of the laser light is absorbed by the material, but the light that passes through or reflected from the material can be used to take super-fast “snapshots” of what is going on in the material following the laser pulse.

Other time-delayed light pulses subsequently hit the material and can be used to take super-fast “snapshots” of what is going on in the material following the laser pulse. The snapshots are replayed afterward like a stop-action movie. One decisive advantage of this approach is the capability to shoot the first frame in less than one trillionth of a second. With the help of successive snapshots and replays,” even the most subtle evolutions in materials’ properties can show their secrets.

Submitted by DOE's Ames Laboratory