paper

Quantum phase transition in the spin-anisotropic quantum spherical model

arXiv:1503.06713 · doi:10.1088/1742-5468/2015/07/P07006

Abstract

Motivated by an analogy with the spin anisotropies in the quantum XY chain and its reformulation in terms of spin-less Majorana fermions, its bosonic analogue, the spin-anisotropic quantum spherical model, is introduced. The exact solution of the model permits to analyse the influence of the spin-anisotropy on the phase diagram and the universality of the critical behaviour in a new way, since the interactions of the quantum spins and their conjugate momenta create new effects. At zero temperature, a quantum critical line is found, which is in the same universality class as the thermal phase transition in the classical spherical model in dimensions. The location of this quantum critical line shows a re-entrant quantum phase transition for dimensions .

34 pages, Latex2e, 3 figures, final form

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