Magnon Landau Levels and Spin Responses in Antiferromagnets (original) (raw)
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Topological Antiferromagnetic Magnons
2019
We have studied a model for a non-collinear but coplanar antiferromagnetic spin texture on a two dimensional kagome lattice structure in the presence of DzyaloshinskiiMoriya Interaction (DMI). We observed some interesting topological properties in our system i.e. the presence of non-trivial edge state in the wave function. This non-trivial edge state, which mainly surfaced in the presence of the DMI, showed robustness against the external magnetic eld and thus can be further studied to see how important transport properties can be computed.
Evidence of Magnon-Mediated Orbital Magnetism in a Quasi-2D Topological Magnon Insulator
Nano Letters
We explore spin dynamics in Cu(1,3-bdc), a quasi-2D topological magnon insulator. The results show that the thermal evolution of Landé g-factor (g) is anisotropic: g in-plane reduces while g out-plane increases with increasing temperature T. Moreover, the anisotropy of the g-factor (∆g) and the anisotropy of saturation magnetization (∆Ms) are correlated below 4 K, but they diverge above 4 K. We show that the electronic orbital moment contributes to the g anisotropy at lower T , while the topological orbital moment induced by thermally excited spin chirality dictates the g anisotropy at higher T. Our work suggests an interplay among topology, spin chirality, and orbital magnetism in Cu(1,3-bdc).
Topological Aspects of Antiferromagnets
Journal of Physics D: Applied Physics, 2021
The long fascination that antiferromagnetic materials has exerted on the scientific community over about a century has been entirely renewed recently with the discovery of several unexpected phenomena, including various classes of anomalous spin and charge Hall effects and unconventional magnonic transport, and also homochiral magnetic entities such as skyrmions. With these breakthroughs, antiferromagnets stand out as a rich playground for the investigation of novel topological behavior, and as promising candidate materials for disruptive low-power microelectronic applications. Remarkably, the newly discovered phenomena are all related to the topology of the magnetic, electronic or magnonic ground state of the antiferromagnets. This review exposes how non-trivial topology emerges at different levels in antiferromagnets and explores the novel mechanisms that have been discovered recently. We also discuss how novel classes of quantum magnets could enrich the currently expanding field ...
Exchange-biasing topological charges by antiferromagnetism
Nature communications, 2018
Geometric Hall effect is induced by the emergent gauge field experienced by the carriers adiabatically passing through certain real-space topological spin textures, which is a probe to non-trivial spin textures, such as magnetic skyrmions. We report experimental indications of spin-texture topological charges induced in heterostructures of a topological insulator (Bi,Sb)Te coupled to an antiferromagnet MnTe. Through a seeding effect, the pinned spins at the interface leads to a tunable modification of the averaged real-space topological charge. This effect experimentally manifests as a modification of the field-dependent geometric Hall effect when the system is field-cooled along different directions. This heterostructure represents a platform for manipulating magnetic topological transitions using antiferromagnetic order.
Physical Review Letters, 2018
We demonstrate that the nontrivial magnetic texture of antiferromagnetic skyrmions (AFM-Sks) promotes a non-vanishing topological spin Hall effect (TSHE) on the flowing electrons. This results in a substantial enhancement of the non-adiabatic torque and hence improves the skyrmion mobility. This non-adiabatic torque increases when decreasing the skyrmion size, and therefore scaling down results in a much higher torque efficiency. In clean AFM-Sks, we find a significant boost of the TSHE close to van Hove singularity. Interestingly, this effect is enhanced away from the band gap in the presence of non-magnetic interstitial defects. Furthermore, unlike their ferromagnetic counterpart, TSHE in AFM-Sks increases with increase in disorder strength thus opening promising avenues for materials engineering of this effect.
Magnon Spin Nernst Effect in Antiferromagnets
Physical Review Letters, 2016
We predict that a temperature gradient can induce a magnon-mediated spin Hall response in an antiferromagnet with non-trivial magnon Berry curvature. We develop a linear response theory which gives a general condition for a Hall current to be well defined, even when the thermal Hall response is forbidden by symmetry. We apply our theory to a honeycomb lattice antiferromagnet and discuss a role of magnon edge states in a finite geometry.
arXiv: Mesoscale and Nanoscale Physics, 2020
We present a comprehensive study on magnon topology in honeycomb bilayer quantum magnets with ferromagnetic (FM) and layered antiferromagnetic (LAFM) ground states. Several models are investigated to fully understand the separate and combined effects of Heisenberg exchange, Kitaev interaction, Dzyaloshinskii-Moriya interaction (DMI), and inversion symmetry breaking. Both ground states constitute rich platforms to realize several topological phases which can be tuned via experimentally controllable parameters. Nevertheless, LAFM bilayers are found to be more exotic: (i) the band gaps can close away from the Brillouin zone corners forming unconventional Dirac cones (UDCs) (ii) the UDCs play a fundamental role in shaping the topological phase diagram in LAFM bilayers and induces richer topology compared to their FM counterparts (iii) valley-polarized magnons can be excited in LAFM bilayers by Zeeman effect (iv) topological phase transitions in LAFM bilayers can reverse the signs of the...
Low Temperature Physics, 2020
Topological charges are calculated for a number of exact three-dimensional analytical solutions to the Landau-Lifshitz equation, which describe the distributions of the vector fields for the vectors of antiferromagnetism and antiferromagnet magnetization. It is shown that in the case of samples with dimensions that are comparable to the characteristic scales of topological objects of the antiferromagnetism and magnetization vector fields, there are modified characteristics that depend not only on the topological properties of these objects, but also on the geometry of the sample. These modified characteristics in samples with finite dimensions may assume non-integer values.