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Quantum description of spherical spins

Th. M. Nieuwenhuizen
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Abstract

The spherical model for spins describes ferromagnetic phase transitions well, but it fails at low temperatures. A quantum version of the spherical model is proposed. It does not induce qualitative changes near the phase transition. However, it produces a physical low temperature behavior. The entropy is non-negative. Model parameters can be adapted to the description of real quantum spins. Several applications are discussed. Zero-temperature quantum phase transitions are analyzed for a ferromagnet and a spin glass in a transversal field. Their crossover exponents are presented.

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Th. M. Nieuwenhuizen. 1995-05-18. Quantum description of spherical spins. https://doi.org/10.1103/physrevlett.74.4293

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