Field-tuned quantum renormalization of spin dynamics in the honeycomb lattice Heisenberg antiferromagnet YbCl

Sala, G.*; Stone, M. B.*; Halsz, G. B.*; Lumsden, M. D.*; Fay, A, F,*; Pajerowski, D. M.*; 河村 聖子; 金子 耕士; Mazzone, D. G.*; Simutis, G.*; et al.

Communications Physics (Internet), 6, p.234_1 - 234_7, 2023/08

https://doi.org/10.1038/s42005-023-01333-7

We demonstrate and elucidate quantum effects on the honeycomb lattice through comprehensive inelastic neutron scattering measurements of the prototype honeycomb lattice quantum magnet YbCl as a function of applied magnetic field. Examining the spectrum above the saturation field where linear spin-wave theory is essentially exact, we accurately determine the dominant nearest-neighbor Heisenberg interaction. Below the saturation field, we reveal a field-dependent energy renormalization of the entire magnetic spectrum; the sharp spin-wave modes as well as the multimagnon continuum. This renormalization is a quantum effect that can be accurately captured by the first 1=S correction in nonlinear spin-wave theory. Furthermore, we find that the application of a magnetic field induces a qualitatively new sharp feature inside the multimagnon continuum; the lower edge of a specific two-magnon component; which is complementary to the previously observed Van Hove singularity and demonstrates that structures within the multimagnon continuum can occur over a wide experimental parameter space and can be used as an additional means of identifying quantum phenomena.