An international research group observed a state in copper oxides in which orbital degrees of freedom did not freeze at low temperatures and electrons fluctuated due to quantum fluctuations. The group also clarified the time scale of these quantum fluctuations in multifrequency electron spin resonance (ESR) experiments in a strong magnetic field for the first time.
Electrons have three degrees of freedom: spin, orbital, and electric charge. In condensed-matter physics, the study of aggregates formed by multiple atoms and ions, such as crystals and glass, the realization of a state of "quantum spin liquid" in which spin degrees of freedom do not freeze even at very low temperatures is thought to be one of the goals in the field.
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