One of the first human inventions is magnetism, which is at the forefront of modern materials that may enable lossless electronics and quantum computers in the future. The discovery could lead to the development of brand-new, effective, and ultra-fast gadgets. Researchers led by Penn State and the University of California, San Diego have found a new “knob” to control the magnetic behavior of one potential quantum material.
“The unique quantum mechanical make-up of this material manganese bismuth telluride allows it to carry lossless electrical currents, something of tremendous technological interest,” said Hari Padmanabhan, who led the research as a graduate student at Penn State.
“What makes this material especially intriguing is that this behavior is deeply connected to its magnetic properties. So, a knob to control magnetism in this material could also efficiently control these lossless currents.”
According to the researchers, manganese bismuth telluride, a 2D material comprised of atomically thin stacked layers, is an example of a topological insulator, an unusual substance that can function as both an electrical conductor and an insulator at the same time. The conductivity of the currents around this material’s edges may be lossless, meaning that they may not waste energy in the form of heat because it is also magnetic.
These functions might be unlocked by finding a means to adjust the weak magnetic connections that connect the material’s layers. The researchers wrote about this on April 8 in the journal Nature Communications. Tiny atom vibrations, or phonons, in the substance may be one way to accomplish this.
“Phonons are tiny atomic wiggles atoms dancing together in various patterns, present in all materials,” Padmanabhan said. “We show that these atomic wiggles can potentially function as a knob to tune the magnetic bonding between the atomic layers in manganese bismuth telluride.”
The researchers at Penn State used a method known as magneto-optical spectroscopy to analyze the material. They fired a laser at a sample of the material and measured the color and intensity of the light that was reflected back, which contained data on the atomic vibrations. The researchers watched how the vibrations evolved as the temperature and magnetic field changed.
The unique quantum mechanical make-up of this material manganese bismuth telluride allows it to carry lossless electrical currents, something of tremendous technological interest. What makes this material especially intriguing is that this behavior is deeply connected to its magnetic properties. So, a knob to control magnetism in this material could also efficiently control these lossless currents.
Hari Padmanabhan
The researchers noticed variations in the phonon intensity when they changed the magnetic field. The phonons’ influence on the tenuous interlayer magnetic bonding, according to the researchers, is what causes this phenomenon.
“Using temperature and magnetic field to vary the magnetic structure of the material much like using a refrigerator magnet to magnetize a needle compass we found that the phonon intensities were strongly correlated with the magnetic structure,” said Maxwell Poore, a graduate student at UC San Diego, and co-author of the study. “Pairing these findings with theoretical calculations, we inferred that these atomic vibrations modify the magnetic bonding across layers of this material.”
Researchers at UC San Diego carried real-time atomic vibration tracking tests out. The scientists claimed that the phonons vibrate more than a trillion times per second, several times faster than current computer circuits. For instance, a computer processor running at 3.5 gigahertz cycles 3.5 billion times per second.
“What was beautiful about this result was that we studied the material using different complementary experimental methods at different institutions and they all remarkably converged to the same picture,” said Peter Kim, a graduate student at UC San Diego, and co-author of the paper.
The experts say more investigation is required before the magnetic knob can be used directly. However, if it is successful, it might result in extremely quick devices that can effectively and irreversibly control lossless currents.
“A major challenge in making faster, more powerful electronic processors is that they heat up,” said Venkatraman Gopalan, professor of materials science and engineering and physics at Penn State, Padmanabhan’s former adviser, and co-author of the paper.
“Heating wastes energy. If we could find efficient ways to control materials that host lossless currents, that would potentially allow us to deploy them in future energy-efficient electronic devices.”
Other Penn State researchers included Seng Huat Lee, an assistant research professor, and Zhiqiang Mao, a professor, from the 2D Crystal Consortium and Department of Physics, as well as Vladimir Stoica, an associate research professor, graduate student Huaiyu “Hugo” Wang, and staff scientist Maxwell Wetherington from the Materials Research Institute and Department of Materials Science and Engineering.
Also contributing were James Rondinelli, professor, Danilo Puggioni, research assistant professor, Mingqiang Gu, postdoctoral scholar, and Nathan Koocher, graduate student, Northwestern University; Xijie Wang, Xiaozhe Shen, and Alexander Reid, staff scientists, SLAC National Accelerator Laboratory; Richard Averitt, professor, University of California, San Diego; Richard Schaller, staff scientist, Argonne National Laboratory; and Aaron Lindenberg, associate professor, Stanford University.
The U.S. Department of Energy, National Science Foundation, and Army Research Office provided funding for this research.
