Damped Topological Magnons in the Kagom\'{e}-Lattice Ferromagnets

We demonstrate that interactions can substantially undermine the free-particle description of magnons in ferromagnets on geometrically frustrated lattices. The anharmonic coupling, facilitated by the Dzyaloshinskii-Moriya interaction, and a highly-degenerate two-magnon continuum yield a strong, non-perturbative damping of the high-energy magnon modes. We provide a detailed account of the effect for the $S=1/2$ ferromagnet on the kagom\'e lattice and propose further experiments.Comment: 4.5 p + 4 figs main, 8 p + 16 figs supplemental, typos correcte

Optimization of Methodological Support of the Tax Benefits Implementation in the Regions: the Practice of the Perm Territory

In the article, the problem of the methodological process support of regional tax benefits is reviewed. The method of tax benefits assessment, accepted in Perm Region, was chosen as an analysis object because the relatively long period of application of benefits has allowed to build enough statistics base. In the article, the reliability of budget, economic, investment, and social effectiveness assessments of application benefits, based on the Method, is investigated. The suggestions of its perfection are formulated

Singlet-triplet Hamiltonian for spin excitation in the Kondo-insulator

Within the framework of periodic asymmetric Anderson model for Kondo isoulators an effective singlet-triplet Hamiltonian with indirect antiferromagnetic f-f exchange interaction is introduced which allows to study analytically the dynamic magnetic susceptibilities of f-electrons. The approach allows to describe the three-level spin excitation spectrum with a specific dispersion in $YbB_{12}$. Distinctive feature of the consideration is the introduction of small radius singlet and triplet collective f-d excitations which at movement on a lattice form low - and high-energy spin bands.Comment: 7 page

Disorder-Induced Mimicry of a Spin Liquid in YbMgGaO4_4

We suggest that a randomization of the pseudo-dipolar interaction in the spin-orbit-generated low-energy Hamiltonian of YbMgGaO$_4$ due to an inhomogeneous charge environment from a natural mixing of Mg$^{2+}$ and Ga$^{3+}$ can give rise to orientational spin disorder and mimic a spin-liquid-like state. In the absence of such quenched disorder, $1/S$ and density matrix renormalization group calculations both show robust ordered states for the physically relevant phases of the model. Our scenario is consistent with the available experimental data and further experiments are proposed to support it.Comment: 5+ main text, 7+ supplemental, text asymptotically close to PR