We directly measure the low energy excitation modes of the quantum Ising magnet LiHoF4 using microwave spectroscopy. Instead of a single electronic mode, we find a set of collective electronuclear modes, in which the spin-1/2 Ising electronic spins hybridize with the bath of spin-7/2 Ho nuclear spins. The lowest-lying electronuclear mode softens at the approach to the quantum critical point, even in the presence of disorder. This softening is rapidly quenched by a longitudinal magnetic field. Similar electronuclear structures should exist in other spin-based quantum Ising systems.
@article{arxiv.2101.05143,
title = {Direct Observation of Collective Electronuclear Modes About a Quantum Critical Point},
author = {M. Libersky and R. D. McKenzie and D. M. Silevitch and P. C. E. Stamp and T. F. Rosenbaum},
journal= {arXiv preprint arXiv:2101.05143},
year = {2022}
}
Comments
12 pages, 5 figures. Accepted for publication in Phys. Rev. Lett