0000000000379586
AUTHOR
Alexander Mook
showing 3 related works from this author
Spurious Symmetry Enhancement and Interaction-Induced Topology in Magnons
2022
Linear spin wave theory (LSWT) is the standard technique to compute the spectra of magnetic excitations in quantum materials. In this paper, we show that LSWT, even under ordinary circumstances, may fail to implement the symmetries of the underlying ordered magnetic Hamiltonian leading to spurious degeneracies. In common with pseudo-Goldstone modes in cases of quantum order-by-disorder these degeneracies tend to be lifted by magnon-magnon interactions. We show how, instead, the correct symmetries may be restored at the level of LSWT. In the process we give examples, supported by nonperturbative matrix product based time evolution calculations, where symmetries dictate that there should be a…
Magnetoelectric Cavity Magnonics in Skyrmion Crystals
2022
We present a theory of magnetoelectric magnon-photon coupling in cavities hosting noncentrosymmetric magnets. Analogously to nonreciprocal phenomena in multiferroics, the magnetoelectric coupling is time-reversal and inversion asymmetric. This asymmetry establishes a means for exceptional tunability of magnon-photon coupling, which can be switched on and off by reversing the magnetization direction. Taking the multiferroic skyrmion-host Cu$_2$OSeO$_3$ with ultralow magnetic damping as an example, we reveal the electrical activity of skyrmion eigenmodes and propose it for magnon-photon splitting of ``magnetically dark'' elliptic modes. Furthermore, we predict a cavity-induced magnon-magnon c…
Zero-frequency chiral magnonic edge states protected by non-equilibrium topology
2023
Topological bosonic excitations must, in contrast to their fermionic counterparts, appear at finite energies. This is a key challenge for magnons, as it prevents straightforward excitation and detection of topologically-protected magnonic edge states and their use in magnonic devices. In this work, we show that in a non-equilibrium state, in which the magnetization is pointing against the external magnetic field, the topologically-protected chiral edge states in a magnon Chern insulator can be lowered to zero frequency, making them directly accessible by existing experimental techniques. We discuss the spin-transfer torque required to stabilize this non-equilibrium state, and show explicitl…