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The theory of the non collinear kagome antiferromangets and its implications

Date : Wednesday, July 20th, 2022 15:00 - 16:00 Place : On Zoom and Main Lecture Room (A632) at ISSP (Hybrid) Lecturer : Dr. Sayak DASGUPTA Affiliation : The University of British Columbia and ISSP Committee Chair : Masaki Oshikawa (ex. 63275)
e-mail: oshikawa@issp.u-tokyo.ac.jp

We construct a field-theoretic description of spin waves in hexagonal antiferromagnets with three magnetic sublattices and coplanar 1200 magnetic order [1]. The three Goldstone modes can be separated by point-group symmetry into a singlet α0 and a doublet β. The α0 singlet is described by the standard theory of a free relativistic scalar field. The field theory of the β doublet is analogous to the theory of elasticity of a two-dimensional isotropic solid with distinct longitudinal and transverse “speeds of sound.” The speeds of sound can be readily calculated for any lattice model. We apply this approach to the compounds of the Mn3X family with stacked kagome layers and extract the exchange coefficients for a model spin Hamiltonian by fitting to neutron scattering data [2]. We then extend our studies to the case of strained system where we show that strain can be used to tune the magnetism and the Hall response of these compounds in both static and dynamic conditions [3,4].

[1] S. Dasgupta and O. Tchernyshyov, Phys. Rev. B 102, 144417 (2020)
[2] Y. Chen et al Phys. Rev. B 102, 054403 (2020)
[3] M. Ikhlas, S. Dasgupta et al, Nature Physics (2022) (accepted)
[4] S. Dasgupta, O. Tretiakov, Communications Physics (in review)

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(Published on: Friday July 15th, 2022)