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Zeeman spectroscopy of vacancy-charge-compensated ${Er}^{3 +}$ sites in ${CaWO}_{4}$ under vector magnetic fields

Fabian Becker , Sudip KC , Lorenz J. J. Sauerzopf , Tim Schneider , Luis Risinger , Christian Schmid , and Kai Müller

TUM School of Computation, Information and Technology, Technical University of Munich, 80333 Munich, Germany; Walter Schottky Institute, Technical University of Munich, 85748 Garching, Germany; and Munich Center for Quantum Science and Technology (MCQST), 80799 Munich, Germany

Phys. Rev. Materials 10, 016203 – Published 8 January, 2026

DOI: https://doi.org/10.1103/mkpd-9r5p

Abstract

We present polarization-resolved optical absorption measurements on ${Er}^{3 +}$ ions in ${CaWO}_{4}$ under vector magnetic fields, focusing on charge-compensated sites arising from local ${Ca}^{2 +}$ vacancies. While the known axial ${Er}^{3 +}$ site displays a single symmetric Zeeman-split transition pattern consistent with $S_{4}$ symmetry, two additional sites exhibit more complex spectral behavior, including sets of transitions that interchange under $90^{\circ}$ crystal rotations-evidence of reduced, rhombiclike symmetry. From these polarization- and temperature-dependent spectra, we extract effective $g$ factors. Our findings are corroborated by electron paramagnetic resonance measurements and support a model of multiple inequivalent ${Ca}^{2 +}$ vacancies around ${Er}^{3 +}$ sites in the host lattice. This detailed characterization contributes to understanding defect-engineered rare-earth sites for quantum information applications.

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Phys. Rev. Materials 10, 016203– Published 8 January, 2026

Vol. 10, Iss. 1 — January 2026

Received 20 October 2025
Accepted 11 December 2025

DOI: https://doi.org/10.1103/mkpd-9r5p

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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Zeeman spectroscopy of vacancy-charge-compensated ${Er}^{3 +}$ sites in ${CaWO}_{4}$ under vector magnetic fields

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Zeeman spectroscopy of vacancy-charge-compensated Er3+ sites in CaWO4 under vector magnetic fields

Abstract

Physics Subject Headings (PhySH)

Article Text

References (37)

Zeeman spectroscopy of vacancy-charge-compensated ${Er}^{3 +}$ sites in ${CaWO}_{4}$ under vector magnetic fields