Physicists Find First Possible 3D Quantum Spin Liquid

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“In a solid with a periodic arrangement of spins, if you know what a spin is doing over here, you can know what a spin is doing many, many repetitions away because of long-range order,” said Rice theoretical physicist and study co-author Andriy Nevidomskyy, an associate professor of physics and astronomy and RCQM member. “In a liquid, on the other hand, there is no long-range order. If you look at two molecules of water a millimeter apart, for example, there is no correlation whatsoever. Nevertheless, due to their hydrogen-hydrogen bonds, they can still have an ordered arrangement at very short distances with nearby molecules, which would be an example of short-range order.”

In 1973, Nobel laureate physicist Philip Anderson proposed the idea of quantum spin liquids based upon the realization that that geometric arrangement of atoms in some crystals could make it impossible for entangled spins to collectively orient themselves in stable arrangements.

As noted science writer Philip Ball aptly described in 2017, “Imagine an antiferromagnet — in which adjacent spins prefer to be oppositely oriented — on a triangular lattice. Each spin has two nearest neighbors in a triangle, but the antiparallel alignment cannot be satisfied for all of the trio. One possibility is that the spin lattice freezes into a disordered ‘glassy’ state, but Anderson showed that quantum mechanics allows the possibility of fluctuating spins even at absolute zero (temperature). This state is called a quantum spin liquid, and Anderson later suggested that it might be connected to high-temperature superconductivity.”

The possibility that quantum spin liquids might explain high-temperature superconductivity spurred widespread interest among condensed matter physicists since the 1980s, and Nevidomskyy said interest further increased when it was “suggested that some examples of so-called topological quantum spin liquids may be amenable to building qubits” for quantum computing.

“But I believe part of the curiosity about quantum spin liquids is that it has resurfaced in many incarnations and theoretical proposals,” he said. “And although we have theoretical models where we know, for a fact, that the result will be a spin liquid, finding an actual physical material that would fulfill those properties has, so far, proven very difficult. There is no consensus in the field, up to now, that any material — 2D or 3D — is a quantum spin liquid.”

Morosan is a professor of physics and astronomy, chemistry, and materials science and nanoengineering at Rice and a member of RCQM.

RCQM leverages global partnerships and the strengths of more than 20 Rice research groups to address questions related to quantum materials. RCQM is supported by Rice’s offices of the provost and the vice provost for research, the Wiess School of Natural Sciences, the Brown School of Engineering, the Smalley-Curl Institute and the departments of Physics and Astronomy, Electrical and Computer Engineering, and Materials Science and NanoEngineering.

Additional study co-authors include Chien-Lung Huang and Haoyu Hu of Rice; Kalyan Sasmal and Brian Maple, both of the University of California, San Diego; Devashibhai Adroja of the United Kingdom’s Rutherford-Appleton Laboratory; Feng Ye, Huibo Cao, Gabriele Sala and Matthew Stone, all of the Neutron Scattering Division at ORNL; Christopher Baines and Joel Barker, both of PSI; Jae-Ho Chung of both Rice and Korea University, Seoul; Xianghan Xu of Rutgers; Manivannan Nallaiyan and Stefano Spagna, both of Quantum Designs Inc. in San Diego; and Gang Chen of both the University of Hong Kong and Fudan University, Shanghai.

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