Magnon dispersion in bilayers of two-dimensional ferromagnets

Ortmanns, Lara C.; Bauer, G.; Blanter, Yaroslav M.

doi:10.1103/physrevb.103.155430

Cited by 8 publications

(3 citation statements)

References 40 publications

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“…Interestingly, we find that a small gap opens at K of the order of % 0.3 meV for AB stacking. Similar gaps have been reported in previous calculations for this stacking configuration [34] and bulk crystals. [35] The projection of the bands shows a change from the low-energy (acoustic) branch and the high-energy (optical) branch at K-point.…”

Section: Magnon Dispersion In Twisted Chromium Trihalidessupporting

confidence: 91%

Domain Wall Formation and Magnon Localization in Twisted Chromium Trihalides

Soriano

2022

Physica Rapid Research Ltrs

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The rise of twistronics revolutionizes the field of condensed matter physics, and more specifically the future applications of 2D materials. At small twist angles, the microscopic world becomes strongly correlated, and unexpected physical phenomena such as superconductivity emerge. For magnetic layers, stacking plays a crucial role in the magnetic exchange coupling between the layers leading to nontrivial spin configurations and flat spin‐wave dispersion when twisted. Herein, a short overview of the most recent theoretical and experimental works reporting the effect of twist angles on 2D magnets is given. In addition, the effect of the twist angle and the local antiferromagnetic interlayer exchange coupling on the formation of antiferromagnetic domains in chromium trihalides is discussed. Finally, some preliminary results on the effect of the stacking and the twist angle on the spin‐wave dispersion of bilayer CrI3 are shown.

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Section: Magnon Dispersion In Twisted Chromium Trihalidessupporting

confidence: 91%

Domain Wall Formation and Magnon Localization in Twisted Chromium Trihalides

Soriano

2022

Physica Rapid Research Ltrs

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“…Moreover, real two-dimensional magnetic systems, like ferromagnetic monolayers, small magnetic anisotropies or dipolar interactions are able to stabilize a long-range magnetic order; see e.g. [131][132][133]. Magnetic excitations in the dilute two-dimensional ferromagnet K 2 Cu 1−x Zn x F 4 have been observed with spin-1/2 for the Cu ions [25].…”

Section: Discussionmentioning

confidence: 99%

Spin-wave theory in a randomly disordered lattice: A Heisenberg ferromagnet

Weiss,

Massih

2022

Preprint

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Starting from the hamiltonian for the Heisenberg ferromagnet which comprise randomly distributed nonmagnetic ions as impurities in a Bravais lattice, we express the spin operators by means of the Dyson-Maleev transformation in terms of the Bose operators of the second quantization. Then by using methods of quantum statistical field theory, we derive the partition function and the free energy for the system. We adopt the Matsubara thermal perturbation method to a portion of the hamiltonian which describes the interaction between magnons and the stationary field of nonmagnetic ions. Upon averaging over all possible distributions of impurities, we express the free energy of the system as a function of the mean impurity concentration. Subsequently, we set up the double-time single particle Green function at temperature T in the momentum space in terms of magnon operators and derive the equation of motion for the Green function through the Heisenberg equation of motion and then solve the resulting equation. From this, we calculate the self-energy and then the spectral density function for the system. We apply the formalism to the case of the simple cubic lattice and compute the density of states, the spectral density function and the lifetime of the magnons as a function of energy for several values of the mean concentration of nonmagnetic ions in the ferromagnetic lattice. We calculate the magnon energy spectrum as a function of the average impurity concentration fraction c, which shows that for low lying states, the excitation energy increases continuously with c in the studied range 0.1 ≤ c ≤ 0.7. We also use the spectral density function to compute some thermodynamical quantities through the magnon occupation number. We have obtained closed form expressions for the configurationally averaged physical quantities of interest in a unified fashion as functions of the mean concentration of nonmagnetic impurities c to any order of c applicable below a critical percolation concentration c p . The quantities of interest comprise the thermodynamic potential (free energy), the spin-wave self-energy and the spectral density function from which other quantities can be derived.

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“…3(a). Two layers are antiferromagnetically coupled, and therefore spins of each layer will be aligned to the opposite directions (ẑ and −ẑ) in the ground state [39,50]. The Hamiltonian can be written in three parts H m,bilayer = H 1 + H 2 + H 12 , where…”

Section: Bilayermentioning

confidence: 99%

Topological phase transition in magnon bands in a honeycomb ferromagnet driven by sublattice symmetry breaking

Kim¹,

Kim²

2022

Preprint

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Ferromagnetic honeycomb systems are known to exhibit a magnonic topological phase under the existence of the next-nearest neighbor Dzyaloshinskii-Moriya interaction (DMI). Motivated by the recent progress in the sublattice-specific control of magnetic anisotropy, we study the topological phase of magnon bands of honeycomb ferromagnetic monolayer and bilayer with the sublattice symmetry breaking due to the different anisotropy energy in the presence of the DMI. We show that there is a topological phase transition between the topological magnon insulator and the topologically trivial magnon phase driven by the change of the relative size of the DMI and the anisotropy differences between the sublattices. The magnon thermal Hall conductivity is proposed as an experimental probe of the magnon topology.

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Magnon dispersion in bilayers of two-dimensional ferromagnets

Cited by 8 publications

References 40 publications

Domain Wall Formation and Magnon Localization in Twisted Chromium Trihalides

Domain Wall Formation and Magnon Localization in Twisted Chromium Trihalides

Spin-wave theory in a randomly disordered lattice: A Heisenberg ferromagnet

Topological phase transition in magnon bands in a honeycomb ferromagnet driven by sublattice symmetry breaking

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