“Quantum spin liquids are the exception,” says Gang Chen, Professor of Physics at Fudan University in China. He is describing the theory Soviet theoretical physicist Lev Landau developed to characterize the ferromagnetic or antiferromagnetic ordering adopted by spins in a magnet when they get too cold to keep fluctuating thermally. Quantum spin liquids shirk this theory. “The spins in quantum spin liquids do not order even down to absolute zero temperature. It is a very exotic quantum phase of matter and cannot be understood in the framework by Landau.”
First proposed in the 1970s, interest in these materials was further piqued in the 1980s at the suggestion that they were the “mother state” for the high-temperature superconductivity in cuprates. More recent reports of a possible quantum spin liquid state in YbMgGaO4 that is robust against weak disorder has rekindled interest. Now in Chinese Physics Letters Chen, alongside Hechang Lei, Qingming Zhang and colleagues in China report a whole diverse family of previously unknown potential quantum spin liquids, opening up a range of opportunities, such as the possibility of tuneable charge gaps and variable exchange coupling, as well as settling some of the confusion around the origin of these exotic states.
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