Robust Optical Coherence in a Chemically Tunable Eu(III) Molecular Crystal

Résumé fourni par la source

Chemical substitution o!ers a powerful route to tune molecular quantum materials, but its e!ects on optical decoherence extend beyond the simple dilution of interacting emitters; here, we investigate these e!ects in the molecular crystal [Eu(III)(TMHD)3(phen)], its dilution series in the isostructural host [Y(TMHD)3(phen)], and a partially deuterated analogue. The optical inhomogeneous linewidth of the 7F0 ↔ 5D0 transition near 580.4 nm exhibits a pronounced concentration dependence, ranging from 6 to 20 GHz, while the transition frequency shifts by up to ↗25 GHz across the dilution series. In contrast, the homogeneous linewidth measured by two-pulse photon echoes remains in the 50–130 kHz regime at 1.4 K, and shows a non-monotonic dependence on Eu(III) content. Partial phenanthroline deuteration also leaves the homogeneous linewidth essentially unchanged. Spectral-di!usion and temperature-dependent photon-echo measurements identify non-magnetic fluctuations of the molecular environment as the dominant residual dephasing channel. In contrast to rigid inorganic rare-earth hosts, the molecular crystal lattice supports low-frequency lattice modes that can dynamically modulate the anisotropic Eu(III) crystal field, while the extrapolated zero-temperature linewidth is most likely limited by electric-field perturbations. These results establish Eu(III) molecular crystals as chemically tunable materials with robust optical coherence and show that chemical dilution simultaneously reshapes static disorder, lattice dynamics, and decoherence, identifying molecular-lattice rigidity and electrostatic stability as central design parame-

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