Abstract-Optical response from the terahertz domain to visible light of electronuclear transitions in LiYF4:Ho3+

G. Matmon, S. A. Lynch, T. F. Rosenbaum, A. J. Fisher, and G. Aeppli

https://journals.aps.org/prb/accepted/f707bK9eF5316d0a710c2a75f5c802098c53e8fb8

Because of its role as a model system with tunable quantum fluctuations and quenched disorder, and the desire for optical control and readout of its states, we have used high resolution optical absorption spectroscopy to measure the crystal field excitations for \mathrm{Ho}3+ ions in \mathrm{LiHo}_x\mathrm{Y}1-x\mathrm{F}_4 from the THz to visible regimes. We show that many of the excitations yield very narrow lines visibly split even by the nuclear hyperfine interaction, making \mathrm{Ho}3+ in \mathrm{LiHo}_x\mathrm{Y}1-x\mathrm{F}_4 a candidate host for optically addressable electro-nuclear qubits with quality factors as high as Q=4.7\times10^5, where the higher lying levels are electronic singlets. Optical transitions in the easily accessible near and mid-infrared are narrow enough to allow readout of the ground state electronuclear qubits responsible for the interesting magnetism of \mathrm{LiHo}_x\mathrm{Y}1-x\mathrm{F}_4. While many of the higher-lying states have been observed previously, we also report here detailed THz domain excitations. The strengths of the electric- and magnetic dipole crystal field transition lines of five of the lowest excited spin-orbit manifolds of dilute LiYF4:Ho3+ were calculated and compared with measurement. The magnitude of the nuclear hyperfine coupling was used to assign the correct upper and lower states to transition lines.