Topological magnon amplification

Abstract

Topology is quickly becoming a cornerstone in our understanding of electronic systems. Like their electronic counterparts, bosonic systems can exhibit a topological band structure, but in real materials it is difficult to ascertain their topological nature, as their ground state is a simple condensate or the vacuum, and one has to rely instead on excited states, for example a characteristic thermal Hall response. Here we propose driving a topological magnon insulator with an electromagnetic field and show that this causes edge mode instabilities and a large non-equilibrium steady-state magnon edge current. Building on this, we discuss several experimental signatures that unambiguously establish the presence of topological magnon edge modes. Furthermore, our amplification mechanism can be employed to power a topological travelling-wave magnon amplifier and topological magnon laser, with applications in magnon spintronics. This work thus represents a step toward functional topological magnetic materials.

Topological magnon insulators in two-dimensional van der Waals ferromagnets CrSiTe 3 and CrGeTe 3 : Toward intrinsic gap-tunability

“…In principle, it is also possible to realize nontrivial topology in a bosonic system, such as a system of magnonic excitations (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), since the band topology can be treated independently from the statistical nature of the particles. Such topological excitations and the corresponding nontrivial in-gap edge states are chiral and robust against disorder; it is thus believed that the emergence and manipulation of the topological magnonic states bare a tremendous promise for future applications in magnonics and topological spintronics, such as, e.g., quantized pumping of magnons (19), spin-wave beam splitter (10), magnon waveguides (20), chiral traveling-wave magnon amplifiers (21), and magnon-driven orbitronics (22). However, in contrast to the case of fermionic systems, the topological excitations have been realized only in very few bosonic systems.…”

Topological wave insulators: a review

“…In this paper, we reviewed recent findings in the field of classical-wave-based topological insulators. While we discussed a few important technology-oriented applications of topological wave insulators in the previous section, there exists a large variety of reports on other relevant applications, including switching [401][402][403][404][405][406][407], modulation [408][409][410], lensing [411], negative refraction [412], sensing [413], beam splitting [414][415][416][417][418], mode locked fiber lasers [419][420][421][422][423][424], delay lines [425][426][427], integrated photonic and phononic devices [428,429], frequency filters [430], frequency converters [431][432][433], interferometers [434], and amplifiers [435,436]. It is important to realize that the advantageous properties of topological wave systems, especially in acoustics, are often mitigated by the presence of dissipation losses, imposing certain restrictions on the available bandwidth of operation or propagation length of the topological edge modes.…”

Topological magnetic excitations

“…Then, control and manipulation of topological magnonic systems can be envisaged which will trigger a new boost to the field. A conceivable way to achieve spatial and temporal control is optical pumping by inverse Faraday effect [159,160] or by parametric pumping [161].…”