Intermediate spin and quantum critical points, etc

TL;DR

This paper explores the concept of intermediate spin in large spin magnets, showing how magnetic fields can tune quantum critical points and induce periodic behavior in physical properties across different dimensions.

Contribution

It introduces a framework for realizing intermediate spin states in large spin magnets and analyzes their quantum critical behavior under magnetic fields.

Findings

Intermediate spin can be realized in large spin magnets.

Magnetic fields control the effective spin and induce periodic physical responses.

Quantum critical regions are periodic in one dimension and point-like in higher dimensions.

Abstract

Unlike that of SO(3) or SU(2), the Lie algebra for SO(2), which defines intermediate spin, comprises only $S_{z}$ and implies $S^{\pm}$ commute. In general, $S_{z}$ has a continuous spectrum. This intermediate spin scheme can realized for the low energy excitations of a wide class of large spin magnets. A magnetic field provides the necessary time reversal symmetry breaking and controls the effective value of the spin $\tilde S$. Physical quantities are periodic in the equilibrium magnetization component induced by this field. In particular for one dimensional antiferromagnets there are periodic regions on the field axis for which the model is quantum critical while in two or three dimensions criticality is reduced to points.