A recent study led by Rice University physicist Qimiao Si sheds light on the mysterious behavior of quantum critical metals — materials that break the usual rules of physics at low temperatures. Published on December 9 in Nature Physics, the research explores quantum critical points (QCPs), where materials hover between two distinct states, such as being magnetic or nonmagnetic. These findings help explain the unique properties of these metals and offer new insights into high-temperature superconductors, which conduct electricity without resistance at relatively high temperatures.
At the heart of the study is quantum criticality, a state where materials become extremely sensitive to quantum fluctuations — tiny disruptions that change how electrons behave. While most metals follow well-established physical laws, quantum critical metals defy these expectations, displaying unusual and collective behaviors that have puzzled scientists for decades. Physicists refer to these systems as “strange metals.”
“Our work dives into how quasiparticles lose their identity in strange metals at these quantum critical points, which leads to unique properties that defy traditional theories,” said Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy and director of Rice’s Extreme Quantum Materials Alliance.
Quasiparticles, representing the collective behavior of electrons acting like individual particles, play a crucial role in energy and information transfer in materials. However, at QCPs, these quasiparticles vanish in a phenomenon known as Kondo destruction. Here magnetic moments in the material cease their usual interaction with electrons, dramatically transforming the metal’s electronic structure.
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