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arXiv · 2601.16362

Nuclear quadrupole interaction and zero first-order Zeeman transitions of $^{167}$Er$^{3+}$ in CaWO$_4$

Lewin Marsh·Yikai Yang·Cesare Mattiroli·Mikhael T. Sayat·Đàm Minh Trí·Henrik M. Rønnow·Jevon J. Longdell·Jian-Rui Soh
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Abstract

We report microwave spectroscopy of $^{167}$Er$^{3+}$ doped in CaWO$_4$ which reveals the hyperfine splitting of the erbium electronic ground state ($Z_1$, $J_\mathrm{eff.}$=15/2) induced by the $I$=7/2 nuclear spin. From spectra measured below$\sim$50 mK in magnetic fields up to 200 mT, we extract spin Hamiltonian parameters including the electron $\textbf{g}$, hyperfine $\textbf{A}$, and nuclear electric quadrupolar $\textbf{Q}$ tensors. Crucially, our analysis demonstrate unambiguously, that the previously unobserved nuclear electric quadrupolar moment is essential to reproduce the experimental data. With these refined parameters, we identify zero first-order Zeeman (ZEFOZ) transitions at zero magnetic field. Extending the analysis to finite fields, we uncover that ZEFOZ points lie either along the $c$ axis or within the $a$-$b$ plane. These results establish CaWO$_4$ as a promising host for long lifetime quantum memories.

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Lewin Marsh, Yikai Yang, Cesare Mattiroli, Mikhael T. Sayat, Đàm Minh Trí, Henrik M. Rønnow, Jevon J. Longdell, Jian-Rui Soh. 2026-01-22. Nuclear quadrupole interaction and zero first-order Zeeman transitions of $^{167}$Er$^{3+}$ in CaWO$_4$. https://doi.org/10.1103/pg5m-hk2n

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