Quantum and classical magnetic Bloch points

Abstract

A Bloch point represents a three-dimensional hedgehog singularity of a magnetic vector field in which the magnetization vanishes. However, standard micromagnetic theory, developed for magnetic moments of fixed lengths, lacks full applicability in studying such singularities. To address this gap, we study a Bloch point in a quantum Heisenberg model for the case of spin-1/2 particles. Performing an exact diagonalization of the Hamiltonian as well as using density matrix renormalization group techniques, we obtain the ground state, which can be used to recover the corresponding magnetization profile. Our findings demonstrate a variation of the spin length in the quantum model, leading smoothly to zero magnetization at the Bloch point. Our results indicate the necessity of generalizing the classical micromagnetic model by adding the third degree of freedom of the spins: the ability to change its length. To this end, we introduce the micromagnetic ${\mathbb{S}}_3$-model, which enables the description of magnets with and without Bloch point singularities.

14 pages, 8 figures

References in corpus (15)

• New type of stable particle like states in chiral magnets (Chiral bobbers)
• Observation of Bloch-point domain walls in cylindrical magnetic nanowires
• Magnetic hopfions in solids
• Multiscale and multimodel simulation of Bloch point dynamics
• Creation of a Chiral Bobber Lattice in Helimagnet-Multilayer Heterostructures
• Coupled quasimonopoles in chiral magnets
• Magnetization structure of a Bloch point singularity
• Pinning of a Bloch point by an atomic lattice
• Screw dislocations in cubic chiral magnets
• Distinct magnetotransport and orbital fingerprints of chiral bobbers
• Quantum Skyrmion Lattices in Heisenberg Ferromagnets
• Discovery of a Bloch point quadrupole constituting hybrid topological strings
• Stable and manipulable Bloch point
• Heliknoton in a film of cubic chiral magnet
• Reconstruction of classical skyrmions from Anderson towers: quantum Darwinism in action

Cited by in corpus (4)

• Stability and Nucleation of Dipole Strings in Uniaxial Chiral Magnets
• Regularized Micromagnetic Theory for Bloch Points
• Energy minima and ordering in ferromagnets with quenched randomness
• Skyrmionic Schrödinger cat states in monoaxial chiral magnets