Abstract
By expanding the gauge λn(k) for magnon band n in harmonics of momentum k=(k,φ), we demonstrate that the only observable component of the magnon orbital angular momentum On(k) is its angular average over all angles φ, denoted by Fn(k). Although Fn(k) vanishes for antiferromagnetic honeycomb and zigzag (0<J1<J2) lattices, it is nonzero for the ferromagnetic (FM) versions of those lattices in the presence of Dzyaloshinskii-Moriya interactions. For a FM zigzag model with equal exchange interactions J1x and J1y along the x and y axes, the magnon bands are degenerate along the boundaries of the Brillouin zone with kx-ky=±π/a and the Chern numbers Cn are not well defined. However, a revised model with J1y≠J1x lifts those degeneracies and produces well-defined Chern numbers of Cn=±1 for the two magnon bands. When J1y=J1x, the thermal conductivity κxy(T) of the FM zigzag lattice is largest for J2/J1>6 but is still about four times smaller than that of the FM honeycomb lattice at high temperatures. Due to the removal of band degeneracies, κxy(T) is slightly enhanced when J1y≠J1x.
| Original language | English |
|---|---|
| Article number | 214402 |
| Journal | Physical Review B |
| Volume | 108 |
| Issue number | 21 |
| DOIs | |
| State | Published - Dec 1 2023 |
Funding
Conversations with Shulei Zhang are gratefully acknowledged. Research by R.F., L.L., and T.B. was sponsored by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. Theoretical contributions by J.V. were supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Science Center. This manuscript has been authored in part by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan .