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Weyl magnons in breathing pyrochlore antiferromagnets

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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.


Related in: MedlinePlus

Surface arc states of a slab.The slab is cleaved along the [110] surface, setting D=0.2J, J′=0.6J and θ=π/2. Γ0 is the origin of the surface Brillouin zone, and two reciprocal lattice vectors are , . The Surface states with E=EWeyl form arcs connecting the projections of Weyl nodes, where EWeyl is the energy of the bulk Weyl nodes. Note each pair of nodes are projected to the same position. Pink (Green) arcs are localized in one (the other) surface.
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f8: Surface arc states of a slab.The slab is cleaved along the [110] surface, setting D=0.2J, J′=0.6J and θ=π/2. Γ0 is the origin of the surface Brillouin zone, and two reciprocal lattice vectors are , . The Surface states with E=EWeyl form arcs connecting the projections of Weyl nodes, where EWeyl is the energy of the bulk Weyl nodes. Note each pair of nodes are projected to the same position. Pink (Green) arcs are localized in one (the other) surface.

Mentions: Finally in Fig. 8, we depict the surface arcs for the [110] surfaces in region II. For this surface, each pair of nodes are projected to the same position, and the surface arcs form two loops across the surface Brillouin zone and connect the Weyl nodes.


Weyl magnons in breathing pyrochlore antiferromagnets
Surface arc states of a slab.The slab is cleaved along the [110] surface, setting D=0.2J, J′=0.6J and θ=π/2. Γ0 is the origin of the surface Brillouin zone, and two reciprocal lattice vectors are , . The Surface states with E=EWeyl form arcs connecting the projections of Weyl nodes, where EWeyl is the energy of the bulk Weyl nodes. Note each pair of nodes are projected to the same position. Pink (Green) arcs are localized in one (the other) surface.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f8: Surface arc states of a slab.The slab is cleaved along the [110] surface, setting D=0.2J, J′=0.6J and θ=π/2. Γ0 is the origin of the surface Brillouin zone, and two reciprocal lattice vectors are , . The Surface states with E=EWeyl form arcs connecting the projections of Weyl nodes, where EWeyl is the energy of the bulk Weyl nodes. Note each pair of nodes are projected to the same position. Pink (Green) arcs are localized in one (the other) surface.
Mentions: Finally in Fig. 8, we depict the surface arcs for the [110] surfaces in region II. For this surface, each pair of nodes are projected to the same position, and the surface arcs form two loops across the surface Brillouin zone and connect the Weyl nodes.

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.


Related in: MedlinePlus