Gaps in topological magnon spectra: Intrinsic versus extrinsic effects
Determining and explaining the presence of a gap at a magnon crossing point is a critical step to characterize the topological properties of a material. An inelastic neutron scattering study of a single crystal is a powerful experimental technique to probe the magnetic excitation spectra of topological materials. Here, we show that when the scattering intensity rapidly disperses in the vicinity of a crossing point, such as a Dirac point, the apparent topological gap size is extremely sensitive to experimental conditions including sample mosaic, resolution, and momentum integration range. In this work, we demonstrate these effects using comprehensive neutron scattering measurements of CrCl3. Our measurements confirm the gapless nature of the Dirac magnon in CrCl3, but also reveal an artificial, i.e., extrinsic, magnon gap unless the momentum integration range is carefully controlled. Our study provides an explanation of the discrepancies between spectroscopic and first-principles estimates of Dirac magnon gap sizes and provides guidelines for accurate measurement of topological magnon gaps.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
- Sponsoring Organization:
- Japan Society for the Promotion of Science (JSPS); USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1883882
- Journal Information:
- Physical Review. B, Journal Name: Physical Review. B Journal Issue: 6 Vol. 106; ISSN 2469-9950
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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