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Weyl magnons in breathing pyrochlore antiferromagnets

View Article: PubMed Central - PubMed

ABSTRACT

Frustrated quantum magnets not only provide exotic ground states and unusual magnetic structures, but also support unconventional excitations in many cases. Using a physically relevant spin model for a breathing pyrochlore lattice, we discuss the presence of topological linear band crossings of magnons in antiferromagnets. These are the analogues of Weyl fermions in electronic systems, which we dub Weyl magnons. The bulk Weyl magnon implies the presence of chiral magnon surface states forming arcs at finite energy. We argue that such antiferromagnets present a unique example, in which Weyl points can be manipulated in situ in the laboratory by applied fields. We discuss their appearance specifically in the breathing pyrochlore lattice, and give some general discussion of conditions to find Weyl magnons, and how they may be probed experimentally. Our work may inspire a re-examination of the magnetic excitations in many magnetically ordered systems.

No MeSH data available.


The spin-wave spectrum of representative points in regions II and III.In the figure, we have chosen the parameters as (a) D=0.6J, J′=0.2J, θ=π/2 and (b) D=0.05J, J′=0.6J, θ=π/3.
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f7: The spin-wave spectrum of representative points in regions II and III.In the figure, we have chosen the parameters as (a) D=0.6J, J′=0.2J, θ=π/2 and (b) D=0.05J, J′=0.6J, θ=π/3.

Mentions: where Jμν and φμν are the same as the ones that are defined for the all-in all-out state. In Fig. 7, we plot the spin-wave spectrum for regions II and III. For region III, there exists a band crossing between a dispersive band and two (degenerate) flat bands from Γ to X. This band crossing may turn into Weyl band touchings if one includes extra spin interactions that make the flat bands non-degenerate and dispersive.


Weyl magnons in breathing pyrochlore antiferromagnets
The spin-wave spectrum of representative points in regions II and III.In the figure, we have chosen the parameters as (a) D=0.6J, J′=0.2J, θ=π/2 and (b) D=0.05J, J′=0.6J, θ=π/3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036007&req=5

f7: The spin-wave spectrum of representative points in regions II and III.In the figure, we have chosen the parameters as (a) D=0.6J, J′=0.2J, θ=π/2 and (b) D=0.05J, J′=0.6J, θ=π/3.
Mentions: where Jμν and φμν are the same as the ones that are defined for the all-in all-out state. In Fig. 7, we plot the spin-wave spectrum for regions II and III. For region III, there exists a band crossing between a dispersive band and two (degenerate) flat bands from Γ to X. This band crossing may turn into Weyl band touchings if one includes extra spin interactions that make the flat bands non-degenerate and dispersive.

View Article: PubMed Central - PubMed

ABSTRACT

Frustrated quantum magnets not only provide exotic ground states and unusual magnetic structures, but also support unconventional excitations in many cases. Using a physically relevant spin model for a breathing pyrochlore lattice, we discuss the presence of topological linear band crossings of magnons in antiferromagnets. These are the analogues of Weyl fermions in electronic systems, which we dub Weyl magnons. The bulk Weyl magnon implies the presence of chiral magnon surface states forming arcs at finite energy. We argue that such antiferromagnets present a unique example, in which Weyl points can be manipulated in situ in the laboratory by applied fields. We discuss their appearance specifically in the breathing pyrochlore lattice, and give some general discussion of conditions to find Weyl magnons, and how they may be probed experimentally. Our work may inspire a re-examination of the magnetic excitations in many magnetically ordered systems.

No MeSH data available.