Magnon Hall effect and topology in kagome lattices: A theoretical investigation

Abstract

Ferromagnetic insulators with Dzyaloshinskii-Moriya interaction show the magnon Hall effect, i.e., a transverse heat current upon application of a temperature gradient. In this theoretical investigation we establish a close connection of the magnon Hall effect in two-dimensional kagome lattices with the topology of their magnon dispersion relation. From the topological phase diagram we predict systems which show a change of sign in the heat current in dependence on temperature. Furthermore, we derive the high-temperature limit of the thermal Hall conductivity; this quantity provides a figure of merit for the maximum strength of the magnon Hall effect. Eventually, we compare the temperature and field dependence of the magnon Hall conductivity of the three-dimensional pyrochlore Lu 2 V 2 O 7 with experimental results.

Magnon Spin Nernst Effect in Antiferromagnets

“…The same effect has also been observed in kagome ferromagnet Cu(1−3, bdc) [27]. The existence of magnon edge states and tunable topology of magnon bands have been discussed theoretically [24,25,[28][29][30][31]. The spin Nernst effect (SNE) has been theoretically studied in Ref.…”

Pumping of magnons in a Dzyaloshinskii-Moriya ferromagnet

“…There is a considerable interest in magnets on lattices with nontrivial geometry as they allow observation of Berry phase related phenomena such as the thermal Hall effect of magnons [32][33][34][35][36][37][38][39][40][41]. Theoretically, the increased magnon damping [42], Dirac magnons [43], and the magnon-mediated spin Hall effect [16,44,45] have been predicted for kagome and honeycomb lattice ferromagnets.…”

Thermal Hall effect of spins in a paramagnet

“…4. A striking parallel of the topology of the magnon band structure to that of electronic bands responsible for quantized Hall effect was emphasized in several recent papers 9,10 . With a solid theoretical foundation and an experimental demonstration to back it up, the thermal Hall effect has become a powerful probe of the topological nature of magnon excitations in an ordered magnet.…”

“…14 Stimulated by their observations, we go beyond the existing magnon description of the thermal Hall effect [4][5][6][7][8][9][10] and formulate the phenomenon using the spin language entirely. It is then applied to discuss Hall effects of spin both in the paramgnetic as well as the ferromagnetic regime.…”