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Physicists find way to entangle topological states with other quantum states

Researchers at Rice University have made an intriguing discovery in the realm of quantum materials. They found that in certain crystal lattices, electrons trapped in atomic orbitals behave similarly to heavy fermions in f orbital systems. This surprising finding establishes a connection between different subfields of physics, particularly between topological materials with “protected” quantum states and strongly correlated materials with unconventional behaviors like and magnetic fluctuations.

The study focused on frustrated lattice arrangements featuring “flat bands,” where electrons become stuck and strongly correlated effects are intensified. The team, led by Qimiao Si and former graduate student Haoyu Hu, developed a quantum model to investigate electron coupling in such arrangements found in metals and semimetals.

The research demonstrated that electrons from d atomic orbitals can join larger molecular orbitals shared by multiple atoms in the lattice. Furthermore, these electrons in molecular orbitals can become entangled with other frustrated electrons, leading to the emergence of familiar strongly correlated effects observed in heavy fermion materials.

This work is part of an ongoing effort by Qimiao Si to establish a theoretical framework for controlling topological states of matter. The results open up new possibilities for entangling immutable topological states with manipulable quantum states in certain materials, which could have significant implications for and spintronics.

Quantum physicist Qimiao Si is Rice University's Harry C. and Olga K. Wiess Professor of Physics and Astronomy and director of the Rice Center for Quantum Materials. Credit: Jeff Fitlow/Rice University

Qimiao Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy at Rice University, explained that while f-electron systems offer clean examples of strongly correlated physics, they are not practical for everyday use due to their very low-temperature requirements (around 10 Kelvin) to observe their effects. He likened this low-temperature physics to a dirt road, far removed from the multilane highway where d-electron systems operate efficiently and couple to each other effectively.

However, Si discovered that even in the presence of a flat band, the d-electron world retains its coupling efficiency. This is akin to one of the highway lanes becoming less efficient, resembling the f-electron dirt road but still maintaining its strong coupling with other lanes. The exciting part is that this coupling efficiency allows for high-temperature physics, potentially around 200 Kelvin or even 300 Kelvin, or at room temperature.

Si sees great promise in this discovery, as it enables exploring the exquisite physics of f-electron systems at much more practical and accessible temperatures. With well-defined models and a wealth of intuition gained from years of studying f-electron materials, the d-electron world offers significant functionality for future applications in quantum materials and technologies.

Source: Rice University

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