Abstract
Topological magnon insulators are the bosonic analogs of electronic topological insulators. They are manifested in magnetic materials with topologically nontrivial magnon bands as realized experimentally in a quasi-two-dimensional (quasi-2D) kagomé ferromagnet Cu(1–3, bdc), and they also possess protected magnon edge modes. These topological magnetic materials can transport heat as well as spin currents, hence they can be useful for spintronic applications. Moreover, as magnons are charge-neutral spin-1 bosonic quasiparticles with a magnetic dipole moment, topological magnon materials can also interact with electromagnetic fields through the Aharonov-Casher effect. In this report, we study photoinduced topological phase transitions in intrinsic topological magnon insulators in the kagomé ferromagnets. Using magnonic Floquet-Bloch theory, we show that by varying the light intensity, periodically driven intrinsic topological magnetic materials can be manipulated into different topological phases with different sign of the Berry curvatures and the thermal Hall conductivity. We further show that, under certain conditions, periodically driven gapped topological magnon insulators can also be tuned to synthetic gapless topological magnon semimetals with Dirac-Weyl magnon cones. We envision that this work will pave the way for interesting new potential practical applications in topological magnetic materials.
Highlights
Topological magnon insulators[6,7,8,9,10,11,12,13,14,15,16,17] are the bosonic analogs of electronic topological insulators
We theoretically investigate photo-irradiated intrinsic topological magnon insulators in the kagomé ferromagnets and their associated topological phase transitions
We achieve this objective by utilizing the quantum theory of magnons, which are charge-neutral spin-1 bosonic quasiparticles and carry a magnetic dipole moment
Summary
Topological magnon insulators[6,7,8,9,10,11,12,13,14,15,16,17] are the bosonic analogs of electronic topological insulators. Recent evidence of topological triplon bands have been reported in a dimerized quantum magnet SrCu2(BO3)[223,24] These magnetic materials have provided an interesting transition from electronic to bosonic topological insulators. One of the main objectives of this report is to induce tunable parameters in intrinsic topological magnon insulators, which subsequently drive the system into a topological phase transition We achieve this objective by utilizing the quantum theory of magnons, which are charge-neutral spin-1 bosonic quasiparticles and carry a magnetic dipole moment. For the periodic time-dependent electric fields (see Methods)[71], this results in a periodically driven magnon system, and can be studied by the Floquet-Bloch theory Using this formalism, we show that intrinsic topological magnon insulators can be tuned from one topological magnon insulator to another with different Berry curvatures, Chern numbers, and thermal Hall conductivity. The magnon spin current in topological magnetic materials can be manipulated by photo-irradiation, which could be a crucial step towards potential practical applications
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