Cottrell Scholar Awards - 2016
A Tale of Two States: Interplay between Magnetism and Superconductivity in Quantum Materials
One of the major goals of theoretical and applied scientists working in condensed matter physics is the discovery of room-temperature superconductors, which would conduct electricity without resistance or heat loss at ambient conditions. These materials, if they can be achieved at all, would doubtless usher in a new era of advanced technological applications, from high-efficiency transmission of electricity in the power grid to powerful medical imaging devices and ultra-sensitive sensors, among many other possibilities.
Rafael Fernandes, an assistant professor in the School of Physics and Astronomy, University of Minnesota, is investigating phenomena that could potentially shed new light in the quest for these exotic materials.
Most metals become superconductors when cooled down. “Superconductors currently have all manner of uses,” Fernandes says. “These uses include everything from MRI scanners to magnetic levitating trains, but their applications are limited.” That’s because ordinary superconductors work only at very low temperatures, usually below -389 F.
About 30 years ago, scientists discovered the first family of so-called “high-temperature” superconductors, which work at temperatures above that of liquid nitrogen (-320 F), a widely used refrigerant. Despite their optimistic name, however, the highest temperature in which these materials operate is about -210 F, which might be considered higher than room temperature on the dark side of the moon, where it’s -243 F, but not on Earth.
Elucidating what makes these materials display “high-temperature” superconductivity remains a challenge, which may hold the key to designing new, higher-temperature superconductors. Fernandes and his research associates are investigating a ubiquitous feature of these systems: the intertwining of superconductivity and another electronic phenomenon, antiferromagnetism. The latter arises because electrons behave as microscopic magnets due to an intrinsic property called “spin.” Antiferromagnetism refers to certain patterns of alignment of these microscopic magnets that are commonly observed in high-temperature superconductors, suggesting an intimate relationship between the two phenomena.
Specifically, Fernandes and his collaborators will explore these phenomena in the copper- and iron-based high-temperature superconductors using advanced computer simulations that employ the so-called Quantum Monte Carlo method. They will also attempt to establish, through modeling, how these states are affected by the strength of the microscopic interactions between the electrons.
“Completion of this work will shed new light on the rich interplay between magnetism and superconductivity,” Fernandes predicts. By advancing our understanding of these two phenomena, the ultimate goal is to provide invaluable insight to guide the discovery of new, exotic and useful materials, such as true room-temperature superconductors.
For the education component of the Cottrell Scholar Award, Fernandes will implement active learning in upper-division undergraduate physics classes. “The goals are to foster the development of skills appealing to students interested in non-academic science and math careers and to enhance the students’ performance and interest,” he said.