Theory of Fractionally-magnetized Quantum Ferromagnet

Abstract

We present a theory to realize entangled quantum spin states with fractional magnetization. The origin of magnetization reduction is partly emergent antiferromagnetism, that is, spin-liquefaction of ferromagnetism. We study a ferromagnetic bilinear coupling region of the spin-$S$ $(\geqq 1)$ bilinear-biquadratic spin chain based on (i) a rigorous eigenstate correspondence between the spin-$S$ model and spin-$\frac{1}{2}$ model and (ii) a numerical exact-diagonalization calculation up to $S=3$. As a result, we obtain a fractional magnetized $M=1-1/(2S)$ phase, where ground states have quantum entanglement-reflecting corresponding spin-$\frac{1}{2}$ antiferromagnetic ground states in a ferromagnetic background. This spin-liquefaction theory of ferromagnets can be generalized to any-dimensional lattices even under a magnetic field. This fractional ferromagnetism opens the new research field of quantum ferromagnets.

References in corpus (3)

• Spin nematic correlations in bilinear-biquadratic S=1 spin chains
• Phase diagram and continuous pair-unbinding transition of the bilinear-biquadratic S=1 Heisenberg chain in a magnetic field
• Continuous quantum phase transition between two topologically distinct valence bond solid states associated with the same spin value

Cited by in corpus (2)

• Ferromagnetic Haldane state and dimer multiplet state of quantum ferromagnets
• Generalization of the Affleck-Kennedy-Lieb-Tasaki Model for Quantum Ferromagnetism