Dec 26 2014
An international team of scientists predicts that a phenomenon known in physics as Fano resonance can exist in materials that are used in electronic devices.
Dawei Wang. Credit: University of Arkansas
The discovery advances the fundamental understanding of ferroelectric relaxors, which were discovered in the early 1960s but whose properties are still poorly understood, said Laurent Bellaiche, a Distinguished Professor of physics at the University of Arkansas.
The study was led by Dawei Wang, a former postdoctoral research associate at the University of Arkansas who is now a professor at Xi’an Jiaotong University in China. With the support of the National Science Foundation, Wang returned to the U of A as a visiting scientist to complete the two-year project.
Bellaiche and Wang study ferroelectric materials, which convert small changes in mechanical energy into electrical energy and vice versa. These changes are known as a piezoelectric response and are used in a wide range of applications that includes cell phones and heart implants.
Wang, a computational physicist, developed and used molecular dynamic computer modeling to perform accurate calculations on a certain type of relaxor, barium zirconium titanium.
The analysis of these results led to the connection between this relaxor’s properties with Fano resonance, a phenomenon in which a narrow discrete state interferes with a continuum of states.
When the discrete and continuum states don’t interfere with each other, there is no resonance. In physics, resonance is the tendency of a system to vary in magnitude or position in a regular manner around a central point with greater amplitude at some frequencies than at others.
“When the states interfere,” Bellaiche said, “you have something very special, which is Fano resonance. Normal relaxors are lead-based. Barium zirconium titanium exhibits these properties but is also lead-free, which is much better for applications such as cell phones.”
The team published its findings on Nov. 5 in Nature Communications, an online journal published by the journal Nature, in a paper titled, “Fano resonance and dipolar relaxation in lead-free relaxors.”
“This was very difficult work and provides a new perspective on the nature of lead-free relaxors,” Wang said. “Determining and analyzing the dielectric response in the relaxor – how the material responds to an oscillating electric field – was the hardest part. We spent a lot of time on that.”
The results were obtained through a collaborative effort with Jirka Hlinka, Petr Ondrejkovic and Jan Petzelt of the Institute of Physics in the Academy of Sciences of the Czech Republic; and Alexei A. Bokov and Zuo-Guang Ye of Simon Fraser University in British Columbia, Canada.
Bellaiche holds the Twenty-First Century Endowed Professorship in Optics/Nanoscience/ Science Education and conducts research in the University of Arkansas’ Institute for Nanoscience and Engineering.
Source: http://www.uark.edu/