Scientists have discovered a new quantum state of matter that connects two significant areas of physics, potentially leading to advancements in computing, sensing and materials science.
A study published in Nature Physics Jan. 14 , co-led by Rice University's Qimiao Si , brings together quantum criticality, where electrons fluctuate between different phases, and electronic topology, which describes a form of quantum organization based on the wave behavior of electrons. The researchers found that strong interactions among electrons can produce topological behavior, paving the way for new technologies that could use this quantum state in real-world applications.
"This is a fundamental step forward," said Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy and director of Rice's Extreme Quantum Materials Alliance . "Our work shows that powerful quantum effects can combine to create something entirely new, which may help shape the future of quantum science."
Connecting criticality and topology
The research team developed a theoretical model predicting how electrons behave when subjected to both strong interactions and topological effects. Quantum criticality typically involves electrons fluctuating between different ordered states, much like water on the cusp of freezing or boiling. Meanwhile, topology concerns the stable "twists" in the wave nature of electrons, which persist even as the material's structure changes.
Traditionally, these quantum phenomena were studied separately. Topology was observed in materials with weak electron interactions, while quantum criticality was prevalent in systems with strongly correlated electrons. The research team aimed to challenge this longstanding separation.
"By merging these fields, we ventured into uncharted territory," said Lei Chen, co-first author of the study and a graduate student at Rice. "We were surprised to find that the quantum criticality itself could generate topological behavior, especially in a setting with strong interactions."
The study didn't stop at the theoretical level. Experimental researchers at the Vienna University of Technology, led by Silke Paschen, co-leader of the study, observed behavior in a heavy fermion material that aligned with the theoretical predictions made by the research team. This material consists of electrons that behave as though they are much heavier due to interactions, showing signs of the new topological quantum state.
Implications for quantum technologies
The relationship between quantum criticality and topology could transform quantum technology by developing devices that are durable and highly sensitive, qualities vital for computing, sensing and low-power electronics.
Topological materials are resistant to disruption, while quantum criticality enhances entanglement, making this hybrid state particularly valuable for managing quantum behavior. Both effects are associated with phenomena such as superconductivity and extreme sensitivity to external signals.
This discovery opens new avenues in the design of quantum materials with significant technological implications.
"The findings address a gap in condensed matter physics by demonstrating that strong electron interactions can give rise to topological states rather than destroy them," Si said. "Additionally, they reveal a new quantum state with substantial practical significance."
Charting a new course in materials science
This discovery provides a road map for identifying or designing new materials that incorporate these quantum properties. The research team's approach suggests looking for materials situated at a quantum critical point that also hold potential for topological structures.
As the researchers delve deeper into this new state of matter, they say they hope to uncover even more unusual quantum behaviors. The ability to combine quantum criticality and topology could transform how scientists approach quantum design and applications.
"Knowing what to search for allows us to explore this phenomenon more systematically," Si said. "It's not just a theoretical insight, it's a step toward developing real technologies that harness the deepest principles of quantum physics."
The study's co-authors include H. Hu of Rice; D.M. Kirschbaum, D.A. Zocco, F. Mazza, M. Karlich, M. Luˇznik, D.H. Nguyen, A. Prokofiev, X. Yan and J. Larrea Jimenez of the Vienna University of Technology; A. M. Strydom of the University of Johannesburg; and D. Adroja of the Rutherford Appleton Laboratory.
The study was supported by the Air Force Office of Scientific Research, the National Science Foundation, the Robert A. Welch Foundation and the Vannevar Bush Faculty Fellowship.
