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arXiv · 2012.09233

Precise determination of low energy electronuclear Hamiltonian for LiY$_{1-x}$Ho$_{x}$F$_{4}$

A. Beckert·R. I. Hermans·M. Grimm·J. R. Freeman·E. H. Linfield·A. G. Davies·M. Müller·H. Sigg·S. Gerber·G. Matmon·G. Aeppli
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Abstract

We use complementary optical spectroscopy methods to directly measure the lowest crystal-field energies of the rare-earth quantum magnet LiY$_{1-x}$Ho$_{x}$F$_{4}$, including their hyperfine splittings, with more than 10 times higher resolution than previous work. We are able to observe energy level splittings due to the $^6\mathrm{Li}$ and $^7\mathrm{Li}$ isotopes, as well as non-equidistantly spaced hyperfine transitions originating from dipolar and quadrupolar hyperfine interactions. We provide refined crystal field parameters and extract the dipolar and quadrupolar hyperfine constants ${A_J=0.02703\pm0.00003}$ $\textrm{cm}^{-1}$ and ${B= 0.04 \pm0.01}$ $\textrm{cm}^{-1}$, respectively. Thereupon we determine all crystal-field energy levels and magnetic moments of the $^5I_8$ ground state manifold, including the (non-linear) hyperfine corrections. The latter match the measurement-based estimates. The scale of the non-linear hyperfine corrections sets an upper bound for the inhomogeneous line widths that would still allow for unique addressing of a selected hyperfine transition. e.g. for quantum information applications. Additionally, we establish the far-infrared, low-temperature refractive index of LiY$_{1-x}$Ho$_{x}$F$_{4}$.

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A. Beckert, R. I. Hermans, M. Grimm, J. R. Freeman, E. H. Linfield, A. G. Davies, M. Müller, H. Sigg, S. Gerber, G. Matmon, G. Aeppli. 2020-12-16. Precise determination of low energy electronuclear Hamiltonian for LiY$_{1-x}$Ho$_{x}$F$_{4}$. https://doi.org/10.1103/physrevb.106.115119

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