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

Abstract

We report microwave spectroscopy of ${}^{167}$Er${}^{3+}$ doped in CaWO${}_4$ which reveals the hyperfine splitting of the erbium electronic ground state ($Z_1$, $J_{eff.}$=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 $\text{g}$, hyperfine $\text{A}$, and nuclear electric quadrupolar $\text{Q}$ 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.

Accepted in PRB

References in corpus (5)

• Coherence time of over a second in a telecom-compatible quantum memory storage material
• Rare-earth solid-state qubits
• Indistinguishable telecom band photons from a single erbium ion in the solid state
• Reducing decoherence in optical and spin transitions in rare-earth-ion doped materials
• Long spin coherence times in the ground state and an optically excited state of ${}^{167}$Er${}^{3+}$:Y${}_2$SiO${}_5$ at zero magnetic field