Fifty years after Anderson's resonating valence-bond proposal, the spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) remains the ultimate platform to explore highly entangled quantum spin states in proximity to magnetic order. Yb-based delafossites are ideal candidate TLHAF materials, which allow experimental access to the full range of applied in-plane magnetic fields. We perform a systematic neutron scattering study of CsYbSe2, first proving the Heisenberg character of the interactions and quantifying the second-neighbour coupling. We then measure the complex evolution of the excitation spectrum, finding extensive continuum features near the 120∘-ordered state, throughout the 1/3-magnetization plateau and beyond this up to saturation. We perform cylinder matrix-product-state (MPS) calculations to obtain an unbiased numerical benchmark for the TLHAF and spectacular agreement with the experimental spectra. The measured and calculated longitudinal spectral functions reflect the role of multi-magnon bound and scattering states. These results provide valuable insight into unconventional field-induced spin excitations in frustrated quantum materials.
@article{arxiv.2210.04928,
title = {Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe$_2$},
author = {Tao Xie and A. A. Eberharter and Jie Xing and S. Nishimoto and M. Brando and P. Khanenko and J. Sichelschmidt and A. A. Turrini and D. G. Mazzone and P. G. Naumov and L. D. Sanjeewa and N. Harrison and A. S. Sefat and B. Normand and A. M. Lauchli and A. Podlesnyak and S. E. Nikitin},
journal= {arXiv preprint arXiv:2210.04928},
year = {2023}
}