Universal spin wavepacket transport in van der Waals antiferromagnets

Abstract

Antiferromagnets (AFMs) are promising platforms for the transmission of quantum information via magnons (the quanta of spin waves), offering advantages over ferromagnets with regard to dissipation, speed of response, and immunity to external fields. Recently, it was shown that in the insulating van der Waals (vdW) semiconductor, CrSBr, strong spin-exciton coupling enables readout of magnon density and propagation using photons of visible light. This exciting observation came with a puzzle: photogenerated magnons were observed to propagate 10${}^3$ times faster than the velocity inferred from neutron scattering, leading to a conjecture that spin wavepackets are carried along by coupling to much faster elastic modes. Here we show, through a combination of theory and experiment, that the propagation mechanism is, instead, coupling within the magnetic degrees of freedom through long range dipole-dipole coupling. This mechanism is an inevitable consequence of Maxwell's equations, and as such, will dominate the propagation of spin at long wavelengths in the entire class of vdW magnets currently under intense investigation. Moreover, identifying the mechanism of spin propagation provides a set of optimization rules, as well as caveats, that are essential for any future applications of these promising systems.

19 pages, 5 figures. arXiv admin note: text overlap with arXiv:2212.03261

References in corpus (7)

• Magnetic 2D materials and heterostructures
• Theoretical prediction of rotating magnon wavepacket in ferromagnets
• Spin Oscillations in Antiferromagnetic NiO Triggered by Circularly Polarized Light
• Magnon transport in quasi-two-dimensional van der Waals antiferromagnets
• Spin waves and magnetic exchange Hamiltonian in CrSBr
• Superfluid spin transport in magnetically ordered solids
• Spin wavepackets in the Kagome ferromagnet Fe${}_3$Sn${}_2$: propagation and precursors

Cited by in corpus (14)

• Magnon-mediated exciton-exciton interaction in a van der Waals antiferromagnet
• Spin-mechanical coupling in 2D antiferromagnet CrSBr
• Fate of entanglement in magnetism under Lindbladian or non-Markovian dynamics and conditions for their transition to Landau-Lifshitz-Gilbert classical dynamics
• Quantum Sensing of Broadband Spin Dynamics and Magnon Transport in Antiferromagnets
• Time-domain study of coupled collective excitations in quantum materials
• Magnetically Modulated Electrical Switching in an Antiferromagnetic Transistor
• Observation of Coherent Ferron Emission and Propagation
• Exciton transport driven by spin excitations in an antiferromagnet
• Spin waves in the bilayer van der Waals magnet CrSBr
• Photoengineering the Magnon Spectrum in an Insulating Antiferromagnet
• Field-induced magnon decays in dipolar quantum magnets
• Understanding the magnetic interactions of the zig-zag honeycomb lattice: Application to $\alpha$-RuCl${}_3$
• Boltzmann transport theory of magnon-exciton drag
• Excitonic optical absorption in strained monolayer CrSBr