Ultrasonic elastic responses in a monopole lattice

The latest experimental advances have extended the scenario of coupling mechanical degrees of freedom in chiral magnets (MnSi/MnGe) to the topologically nontrivial skyrmion crystal and even monopole lattices. Equipped with a spin-wave theory highlighting the topological features, we devise an intera...

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Bibliographic Details
Published in:New journal of physics 2017-04, Vol.19 (4), p.43012
Main Authors: Zhang, Xiao-Xiao, Nagaosa, Naoto
Format: Article
Language:English
Subjects:
Coupling
Crystal defects
Crystal lattices
Elastic anisotropy
Fine structure
Hypothetical particles
magnetoelastic interaction
Magnets
Magnons
Modulus of elasticity
Monopoles
Particle theory
Phase transitions
Physics
skyrmion/monopole lattice
Sound waves
topological phase transition
Topology
ultrasonic response
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Summary:The latest experimental advances have extended the scenario of coupling mechanical degrees of freedom in chiral magnets (MnSi/MnGe) to the topologically nontrivial skyrmion crystal and even monopole lattices. Equipped with a spin-wave theory highlighting the topological features, we devise an interacting model for acoustic phonons and magnons to explain the experimental findings in a monopole lattice with a topological phase transition, i.e. annihilation of monopole-antimonopole pairs. We reproduce the anisotropic magnetoelastic modulations of elastic moduli: drastic ultrasonic softening around the phase transition and a multi-peak-and-trench fine structure for sound waves parallel and orthogonal to the magnetic field, respectively. Comparison with experiments indicates that the magnetoelastic coupling induced by Dzyaloshinskii-Moriya interaction is comparable to that induced by the exchange interaction. Other possibilities such as elastic hardening are also predicted. The study implies that the monopole defects and their motion in MnGe play a crucial role.
ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/aa6322