Rice physicists trace quantum entanglement in strange metal
by Clarence Oxford
Los Angeles CA (SPX) Apr 01, 2025

Physicists at Rice University have taken a major step toward explaining the puzzling nature of strange metals, a class of materials that defy traditional understandings of electrical and magnetic behavior. By applying a concept from quantum information science known as quantum Fisher information (QFI), the team revealed that electrons in strange metals become maximally entangled at a key phase transition, offering new insights into their complex behavior. The findings, recently published in Nature Communications, could inform the development of advanced superconducting technologies.

Unlike ordinary metals like gold or copper, whose electrical conductance is well described by established physical laws, strange metals operate under a different set of rules. Their resistance behaves anomalously, especially at low temperatures, and has remained one of condensed matter physics' most enduring mysteries. Led by Qimiao Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy at Rice, the team used QFI to explore the intricate dynamics of electron interactions.

The research shows that entanglement among electrons intensifies dramatically at a quantum critical point-a boundary between two different phases of matter. This result sheds light on why traditional descriptions break down for strange metals.

"Our findings reveal that strange metals exhibit a unique entanglement pattern, which offers a new lens to understand their exotic behavior," Si explained. "By leveraging quantum information theory, we are uncovering deep quantum correlations that were previously inaccessible."

To probe this phenomenon, the researchers studied a theoretical construct known as the Kondo lattice, which models how localized magnetic moments interact with mobile electrons. As the system approaches the critical point, these interactions become so strong that the quasiparticles-the standard carriers of electric current-cease to exist. Through their application of QFI, the team demonstrated that this loss is directly linked to a peak in quantum entanglement.

This approach marks a novel fusion of quantum information science and condensed matter physics. It opens new possibilities for examining complex materials through a fundamentally different theoretical framework.

"By integrating quantum information science with condensed matter physics, we are pivoting in a new direction in materials research," Si said.

Theoretical predictions from the Rice team also coincided with data from inelastic neutron scattering experiments, a method used to observe atomic-level interactions in materials. This convergence supports the idea that electron entanglement is not just a theoretical construct but a measurable feature influencing material behavior.

Beyond advancing fundamental understanding, the research may have practical implications. Strange metals are closely linked to high-temperature superconductors, materials that can conduct electricity without energy loss. Unlocking the mysteries of strange metals could accelerate the development of energy-efficient technologies and reshape modern power distribution systems.

Moreover, the study demonstrates how techniques from quantum information science can be extended to other unconventional materials, potentially benefiting the future of quantum computing and advanced electronics. By identifying when and how entanglement reaches its maximum, the research provides a roadmap for investigating materials with unusual quantum properties.

Research Report:Amplified multipartite entanglement witnessed in a quantum critical metal

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