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Physical Review Letters

Phonon-bottlenecked spin relaxation of Er 3 + :CaWO 4 at milliKelvin temperatures

S. Rajendran, B. Mistri, P. K. Sharma, S. E. Kubatkin, A. V. Danilov, S. Dhomkar, Sebastian E. de Graaf, V. Ranjan

Published Oct 21, 2026• 0 citations
Publisher
DOI
10.1103/j1w1-36cy

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Coupling between CaWO4_44​ phonons and Er3+^{3+}3+ dopants
We investigate the lattice dynamics of CaWO4_44​, a promising host crystal for erbium-based quantum memories, using inelastic neutron scattering together with density-functional perturbation theory. The measured phonon dispersion along the (100), (001), and (101) reciprocal space direction reveals phonon bands extending up to 130 meV, with a gap between 60 and 80 meV, in good agreement with our calculations. From a symmetry analysis of the phonon eigenmodes, we identify eight Raman-active modes that can couple directly to the Er3+^{3+}3+ crystal-field operators, including a low-energy BgB_gBg​ mode at 9.1 meV that is expected to play a dominant role in phonon-assisted spin-lattice relaxation. These results provide a microscopic description of the phonon bath in CaWO4_44​ and establish a basis for engineering phononic environments to mitigate the loss of stored quantum states and optimize Er-doped CaWO4_44​ for quantum-memory applications.
Isotopically enriched epitaxial CaWO4_{4}4​ thin films for Er3+^{3+}3+ spin-photon quantum interfaces
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