Team leverages OSC services to help confirm, interpret experimental findings
Phonons--the elemental particles that transmit both heat and sound--have magnetic properties, according to a landmark study supported by Ohio Supercomputer Center (OSC) services and recently published by a researcher group from The Ohio State University.
A team led by Ohio State's Wolfgang Windl, Ph.D., used OSC's Oakley Cluster to calculate acoustic phonon movement within an indium-antimonide semiconductor under a magnetic field. Their findings show that phonon amplitude-dependent magnetic moments are induced on the atoms, which change how they vibrate and transport heat.
In a recent issue of the journal Nature Materials, the researchers describe how a magnetic field, roughly the size of a medical MRI, reduced the amount of heat flowing through a semiconductor by 12 percent. Simulations performed at OSC then identified the reason for it--the magnetic field induces a diamagnetic response in vibrating atoms known as phonons, which changes how they transport heat.
"This adds a new dimension to our understanding of acoustic waves," said Joseph Heremans, Ph.D., Ohio Eminent Scholar in Nanotechnology and a professor of mechanical engineering at Ohio State whose group performed the experiments. "We've shown that we can steer heat magnetically. With a strong enough magnetic field, we should be able to steer sound waves, too."
People might be surprised enough to learn that heat and sound have anything to do with each other, much less that either can be controlled by magnets, Heremans acknowledged. But both are expressions of the same form of energy, quantum mechanically speaking. So any force that controls one should control the other.
The nature of the effect of the magnetic field initially was not understood and subsequently was investigated through computer simulations performed on OSC's Oakley Cluster by Oscar Restrepo, Ph.D., a research associate, Nikolas Antolin, a doctoral student, and Wolfgang Windl, Ph.D., a professor, all of Ohio State's Department of Materials Science and Engineering. After painstakingly examining all possible magnetic responses that a non-magnetic material can have to an external field, they found that the effect is due to a diamagnetic response, which exists in all materials. This suggests then that the general effect should be present in any solid.
The implication: in materials such as glass, stone, plastic--materials which are not conventionally magnetic--heat can be controlled magnetically, if you have a powerful enough magnet. This development may have future impacts on new energy production processes.
But, there won't be any practical applications of this discovery any time soon: seven-tesla magnets like the one used in the study don't exist outside of hospitals and laboratories, and a semiconductor made of indium antimonide had to be chilled to -450 degrees Fahrenheit (-268 degrees Celsius)--very close to absolute zero--to make the atoms in the material slow down enough for the phonons' movements to be detectible.
To simulate the experiment, Windl and his computation team employed a quantum mechanical modeling strategy known as density functional theory (DFT). The DFT strategy was used to determine how the electron distribution changed when atoms vibrated with or without magnetic field. The motion of the electrons around their atoms changed in the field, creating diamagnetic moments when phonons were present. These moments then reacted to the field and slowed the heat transport, similar to an eddy current brake in a train.
The simulations were conducted on the Oakley Cluster, an HP/Intel Xeon system with more than 8,300 processor cores to provide researchers with a peak performance of 154 Teraflops--tech-speak for 154 trillion calculations per second. Since atoms can vibrate in many different ways, a large number of simulations were necessary, consuming approximately 1.5 million CPU hours even on a machine as powerful as Oakley. OSC engineers also helped the research team use OSC's high-throughput, parallel file system to handle the immense datasets generated by the DFT model.
"OSC offered us phenomenal support; they supported our compilation and parallel threading issues, helped us troubleshoot hardware issues when they arose due to code demands, and moved us to the Lustre high-performance file system after we jammed their regular file system," said Antolin, who is the expert for high-demand computations in Windl's group.
"Dr. Windl and his team are important OSC clients, and we're always pleased to support their research projects with our hardware, software and staff support services," said David Hudak, Ph.D., OSC's director of supercomputer services. "With the addition of the Ruby Cluster this past fall and another, much more powerful system upcoming this fall, OSC will continue to offer even larger, faster and more powerful services to support this type of discovery and innovation."
Next, the group plans to test whether they can deflect sound waves sideways with magnetic fields.
Coauthors on the study included graduate student Hyungyu Jin and postdoctoral researcher Stephen Boona from mechanical and aerospace engineering; and Roberto Myers, Ph.D., an associate professor of materials science and engineering, physics and mechanical and aerospace engineering.
Funding for the study came from the U.S. Army Research Office, the U.S. Air Force Office of Scientific Research and the National Science Foundation (NSF), including funds from the NSF Materials Research Science and Engineering Center at Ohio State. Computing services were provided by the Ohio Supercomputer Center.
Jamie Abel | EurekAlert!
Argon is not the 'dope' for metallic hydrogen
24.03.2017 | Carnegie Institution for Science
Researchers make flexible glass for tiny medical devices
24.03.2017 | Brigham Young University
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy