Anomalous spin wave excitations in quantum antiferromagnets CsFeCl3 and RbFeCl3
e-mail: masuda@issp.u-tokyo.ac.jpLanguage in Speech : English
The alkali-metal trichloroferrates AFeCl3 (A = Cs and Rb) are prototypical S = 1 triangular quantum antiferromagnets with strong planar magnetic anisotropy [1]. Under the influence of hydrostatic pressure [2] or chemical composition [3], they are known to exhibit quantum phase transitions between gapped quantum-paramagnetic and magnetically ordered states. A combination of quantum criticality and geometrical frustration makes spin dynamics in AFeCl3 complex and intriguing. However, a comprehensive understanding is still lacking. In this talk, I present a detailed quantitative analysis of the spin-wave excitations by neutron scattering technique [2,3] and the extended spin-wave theory (ESWT) [4]. The spin-wave analysis seems to work reasonably well for CsFeCl3, but the ESWT fails already on a quantitative level for RbFeCl3. The most striking finding is that the measured spin-wave intensity is highly anisotropic in the long-wavelength limit, whereas the ESWT simulation based on short-range interaction alone predicts an isotropic spectrum. We conclude that this discrepancy is attributed to long-range dipolar interactions [5].
References
[1] H. Yoshizawa et al., J. Phys. Soc. Jpn. 49, 144 (1980). [2] S. Hayashida et al., Sci. Adv. 5, eaaw5639 (2019). [3] S. Hayashida et al., Phys. Rev. B 99, 224420 (2019). [4] M. Matsumoto, S. Hayashida, and T. Masuda, J. Phys. Soc. Jpn. 89, 034710 (2020). [5] L. Stoppel, S. Hayashida et al., Phys. Rev. B 104, 094422 (2021).