Oak Ridge National Laboratory



Media Contact: Carolyn Krause ()
Communications and External Relations


SNS user from Johns Hopkins excited by first-day data

OAK RIDGE, Tenn., Dec. 28, 2010 — Collin Broholm, a professor of physics at Johns Hopkins University in Baltimore, was clearly excited about the results he was reviewing in the control room of the wide-angular-range chopper spectrometer (ARCS) at SNS.

He is the principal investigator for three experiments to be run on ARCS on recently discovered materials. Broholm had arrived at the SNS at 10:30 a.m. for the start of one experiment, and by 3 p.m., colorful plots and images on the computer screens were yielding valuable new information.

"I am pleasantly surprised and impressed by the quality and quantity of data we have received in such a short time," he said, referring also to his graduate student Jia Jia Wen and ARCS instrument scientist Matt Stone (who also once studied under Broholm). "We already have an image. The quantity of the data is excellent and so important for untangling the intricate effects of magnetism on the atomic scale.

"For us the outcome of this experiment is very exciting," Broholm added. "The details are still emerging and we don't know what it means yet, but it could be very interesting."

Broholm and his colleagues are conducting basic research on new antiferromagnetic materials discovered and synthesized at the Institute for Quantum Matter (IQM), a joint venture of Johns Hopkins and Princeton Universities, and at the Institute for Solid State Physics in Japan.

They are interested in the fundamental physics of novel materials, in particular correlated behavior among electron spins and the formation of correlated spin clusters. At ARCS that day, they used neutrons to measure changes in the collective behavior of electron spins, the spatial arrangement of the spins, and fluctuation frequencies of the spins (how often per time unit an electron spin direction flips) when the temperature of the sample is raised slowly from 5 to 200 Kelvin. (See The" target="_blank">http://www.ornl.gov/info/features/get_feature.cfm?FeatureNumber=f20101228-03">The Spin Doctor for more details.)

Although the research group is focused on fundamental physics, Broholm said that findings in this area of research could lead to practical applications in the next couple of decades. "By suppressing conventional magnetic order it might be possible to promote superconductivity at temperatures closer to room temperature," Broholm said. "A longer-term application might be quantum computing."

Unlike a personal computer, which makes one calculation at a time, a quantum computer can perform many calculations simultaneously through the magic of quantum coherence. Such a powerful computer, with massively parallel processing, would be useful for defense purposes, such as deciphering encrypted codes, but the most important applications cannot yet be predicted.

In other experiments at SNS on novel materials, Broholm's group is using the Cold Neutron Chopper Spectrometer to probe low-energy fluctuations of electron spins and POWGEN (a powder diffractometer) to learn the details of their crystal and magnetic structures.

Since the 1990s Broholm has been involved in the evolution of the SNS project as a workshop participant, scientific advisor, and panel member. "For years I looked forward to this day when we can actually do experiments," he said. "We are extremely excited by the possibilities we now see and are incorporating SNS into our scientific program."

Broholm has discovered another benefit of the SNS. The experiments he is doing with graduate students, postdocs, and ORNL staff researchers give him a short reprieve from teaching Physics 101 to more than 300 undergraduate students. He wouldn't say whether he has observed correlated behavior and clusters in his classes.