Abstract
Unlike the Berry phase, the orbital angular momentum (OAM) of magnons with two-dimensional wave vector k in band n is not gauge invariant for arbitrary phase λn(k) and so is not physically observable. However, by integrating the OAM over the orientation φ of wave vector k, we construct a gauge-invariant function Fn(k). Like Fn(k), the average OAM for magnon band n in a circle of radius k is also gauge invariant and can be directly observed. We demonstrate these results for a ferromagnet on a honeycomb lattice with Dzyalloshinskii-Moriya interactions between next-nearest neighbor spins. With wave vectors k restricted to the first Brillouin zone, the angular averaged OAM Fn(k) then has opposite signs for lower and upper bands n=1 and 2 for all k.
| Original language | English |
|---|---|
| Article number | 214434 |
| Journal | Physical Review B |
| Volume | 107 |
| Issue number | 21 |
| DOIs | |
| State | Published - Jun 1 2023 |
Funding
ORNL is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the US Department of Energy. The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this article, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan . Satoshi Okamoto and Giovanni Vignale helped this work with useful conversations. Research was sponsored by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | DE-AC05-00OR22725 |
| Division of Materials Sciences and Engineering |