Singly occupied 4$f$ antiferromagnetic insulators: CePO${}_4$ and CeVO${}_4$

Abstract

Rare-earth containing wide band gap oxides, which provide spin-photon interface and narrow linewidth optical emission, are getting significant attention as the most promising candidate materials in advancing quantum transduction and memories. Here, from $abinitio$ calculations, we identify antiferromagnetic ground states in structurally preferred monoclinic CePO${}_4$ and tetragonal CeVO${}_4$ exhibiting localized occupied and unoccupied Ce $4f$ states with $4f-4f$ transition characteristics. Interestingly, in CePO${}_4$, O $2p$ and P $3p$ states hybridize negligibly with Ce $4f$ states, while in CeVO${}_4$, V $3d$ and O $2p$ states hybridize and appear as extended states in between the occupied and unoccupied Ce $4f$ states. Here, phonon calculations and analysis identify and differentiate Raman active phonon modes along with the spin phonon coupling of Ce in both CePO${}_4$ and CeVO${}_4$ that ultimately lead to different $4f$ ground state crystal field multiplets, which are critical to accurately describe electronic transitions for foundational quantum transduction and memories. Further, the identified $C_1$ site symmetry of Ce, lacking inversion symmetry in CePO${}_4$, is relevant for quantum memories and $D_{2d}$ site symmetry of Ce exhibiting inversion symmetry in CeVO${}_4$ is relevant for quantum transduction.

9 pages, 4 figures, 1 table