Theory of magnons in spin systems with Dzyaloshinskii–Moriya interaction

Hog, Sahbi El; Diep, H. T.; Puszkarski, H.

doi:10.1088/1361-648x/aa75a4

Cited by 12 publications

(6 citation statements)

References 37 publications

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“…In order to use the Holstein-Primakoff transformations in Eqs. (28) and (30), we must therefore write the Hamiltonian in terms of this new basis. If R(θ) is the rotation matrix in the x − y plane, i.e.,…”

Section: Discussionmentioning

confidence: 99%

“…In this paper, we will study a system consisting of spins on a kagome lattice with anisotropic XXZ and Dzyaloshinskii-Moriya interactions between nearestneighbor spins. (While the effects of Dzyaloshinskii-Moriya interactions have been extensively studied earlier 28 , the combined effects of XXZ and Dzyaloshinskii-Moriya interactions have not been investigated as thoroughly; however, see Refs. 26,27).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Topological magnons in a kagome-lattice spin system with XXZ and Dzyaloshinskii-Moriya interactions

Seshadri

Sen

2018

Phys. Rev. B

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We study the phases of a spin system on the kagome lattice with nearest-neighbor XXZ interactions with anisotropy ratio ∆ and Dzyaloshinskii-Moriya interactions with strength D. In the classical limit where the spin S at each site is very large, we find a rich phase diagram of the ground state as a function of ∆ and D. There are five distinct phases which correspond to different groundstate spin configurations in the classical limit. We use spin-wave theory to find the bulk energy bands of the magnons in some of these phases. We also study a strip of the system which has infinite length and finite width; we find states which are localized near one of the edges of the strip with energies which lie in the gaps of the bulk states. In the ferromagnetic phase in which all the spins point along the +ẑ or −ẑ direction, the bulk bands are separated from each other by finite energy gaps. This makes it possible to calculate the Berry curvature at all momenta, and hence the Chern numbers for every band; the number of edge states is related to the Chern numbers. Interestingly, we find that there are four different regions in this phase where the Chern numbers are different. Hence there are four distinct topological phases even though the ground-state spin configuration is identical in all these phases. We calculate the thermal Hall conductivity of the magnons as a function of the temperature in the above ferromagnetic phase; we find that this can distinguish between the various topological phases. These results are valid for all values of S. In the other phases, there are no gaps between the different bands; hence the edge states are not topologically protected.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Topological magnons in a kagome-lattice spin system with XXZ and Dzyaloshinskii-Moriya interactions

Seshadri

Sen

2018

Phys. Rev. B

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“…Concurrently, spin waves have been explored for their potential application in spintronic and magnonic devices [15][16][17][18][19]. However, the behavior of spin waves in these noncollinear systems is only now beginning to be understood [20][21][22][23][24][25][26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets

et al. 2018

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Topological noncollinear magnetic phases of matter are at the heart of many proposals for future information nanotechnology, with novel device concepts based on ultrathin films and nanowires. Their operation requires understanding and control of the underlying dynamics, including excitations such as spin waves. So far, no experimental technique has attempted to probe large wave-vector spin waves in noncollinear low-dimensional systems. In this paper, we explain how inelastic electron scattering, being suitable for investigations of surfaces and thin films, can detect the collective spin-excitation spectra of noncollinear magnets. To reveal the particularities of spin waves in such noncollinear samples, we propose the usage of spin-polarized electron-energy-loss spectroscopy augmented with a spin analyzer. With the spin analyzer detecting the polarization of the scattered electrons, four spin-dependent scattering channels are defined, which allow us to filter and select specific spin-wave modes. We take as examples a topological nontrivial skyrmion lattice, a spin-spiral phase, and the conventional ferromagnet. Then we demonstrate that, counterintuitively and in contrast to the ferromagnetic case, even non-spin-flip processes can generate spin waves in noncollinear substrates. The measured dispersion and lifetime of the excitation modes permit us to fingerprint the magnetic nature of the substrate.

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“…Here let us show theoretically spin-waves (SW) excited in the magnetic film in zero field, in some simple cases of the simple cubic lattice. The method we employ is the Green’s function technique for non collinear spin configurations which has been shown to be efficient for studying low- T properties of quantum spin systems such as helimagnets [ 48 ] and systems with a DM interaction [ 49 ]. This technique is rather lengthy to describe here.…”

Section: Spin Wavesmentioning

confidence: 99%

Skyrmions and Spin Waves in Magneto–Ferroelectric Superlattices

Sharafullin

Diep

2020

Entropy

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We present in this paper the effects of Dzyaloshinskii–Moriya (DM) magneto–electric coupling between ferroelectric and magnetic interface atomic layers in a superlattice formed by alternate magnetic and ferroelectric films. We consider two cases: magnetic and ferroelectric films have the simple cubic lattice and the triangular lattice. In the two cases, magnetic films have Heisenberg spins interacting with each other via an exchange J and a DM interaction with the ferroelectric interface. The electrical polarizations of ±1 are assumed for the ferroelectric films. We determine the ground-state (GS) spin configuration in the magnetic film and study the phase transition in each case. In the simple cubic lattice case, in zero field, the GS is periodically non collinear (helical structure) and in an applied field H perpendicular to the layers, it shows the existence of skyrmions at the interface. Using the Green’s function method we study the spin waves (SW) excited in a monolayer and also in a bilayer sandwiched between ferroelectric films, in zero field. We show that the DM interaction strongly affects the long-wave length SW mode. We calculate also the magnetization at low temperatures. We use next Monte Carlo simulations to calculate various physical quantities at finite temperatures such as the critical temperature, the layer magnetization and the layer polarization, as functions of the magneto–electric DM coupling and the applied magnetic field. Phase transition to the disordered phase is studied. In the case of the triangular lattice, we show the formation of skyrmions even in zero field and a skyrmion crystal in an applied field when the interface coupling between the ferroelectric film and the ferromagnetic film is rather strong. The skyrmion crystal is stable in a large region of the external magnetic field. The phase transition is studied.

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Theory of magnons in spin systems with Dzyaloshinskii–Moriya interaction

Cited by 12 publications

References 37 publications

Topological magnons in a kagome-lattice spin system with XXZ and Dzyaloshinskii-Moriya interactions

Topological magnons in a kagome-lattice spin system with XXZ and Dzyaloshinskii-Moriya interactions

Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets

Skyrmions and Spin Waves in Magneto–Ferroelectric Superlattices

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