Philip Anderson, a leading theorist, first proposed the concept in 1987, saying that this state could be relevant to high-temperature superconductors, Lee says. "Ever since then, physicists have wanted to make such a state," he adds. "It's only in the past few years that we've made progress."
The material itself is a crystal of a mineral called herbertsmithite. Lee and his colleagues first succeeded in making a large, pure crystal of this material last year a process that took 10 months and have since been studying its properties in detail.
"This was a multidisciplinary collaboration, with physicists and chemists," Lee explains. "You need both to synthesize the material and study it with advanced physics techniques. Theorists were also crucial to this."
Through its experiments, the team made a significant discovery, Lee says: They found a state with fractionalized excitations, which had been predicted by some theorists but was a highly controversial idea. While most matter has discrete quantum states whose changes are expressed as whole numbers, this QSL material exhibits fractional quantum states. In fact, the researchers found that these excited states, called spinons, form a continuum. This observation, they say in their Nature paper, is "a remarkable first."
To measure this state, the team used a technique called neutron scattering, which is Lee's specialty. To actually carry out the measurements, they used a neutron spectrometer at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md.
The results, Lee says, are "really strong evidence of this fractionalization" of the spin states. "That's a fundamental theoretical prediction for spin liquids that we are seeing in a clear and detailed way for the first time."
It may take a long time to translate this "very fundamental research" into practical applications, Lee says.
|Contact: Caroline McCall|
Massachusetts Institute of Technology