We report thermodynamic and neutron scattering measurements of the triangular-lattice quantum Ising magnet TmMgGaO 4 in longitudinal magnetic fields. Our experiments reveal a quasi-plateau state induced by quantum fluctuations. This state exhibits an unconventional non-monotonic field and temperature dependence of the magnetic order and excitation gap. In the high field regime where the quantum fluctuations are largely suppressed, we observed a disordered state with coherent magnon-like excitations despite the suppression of the spin excitation intensity. Through detailed semi-classical calculations, we are able to understand these behaviors quantitatively from the subtle competition between quantum fluctuations and frustrated Ising interactions.
@article{arxiv.2011.09376,
title = {Field-Tuned Quantum Effects in a Triangular-Lattice Ising Magnet},
author = {Yayuan Qin and Yao Shen and Changle Liu and Hongliang Wo and Yonghao Gao and Yu Feng and Xiaowen Zhang and Gaofeng Ding and Yiqing Gu and Qisi Wang and Shoudong Shen and Helen C. Walker and Robert Bewley and Jianhui Xu and Martin Boehm and Paul Steffens and Seiko Ohira-Kawamura and Naoki Murai and Astrid Schneidewind and Xin Tong and Gang Chen and Jun Zhao},
journal= {arXiv preprint arXiv:2011.09376},
year = {2021}
}