Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA.
Department of Physics, Florida A&M University, Tallahassee, FL, 32307, USA.
Nat Commun. 2018 Jul 3;9(1):2572. doi: 10.1038/s41467-018-04896-0.
Spin-phonon coupling plays an important role in single-molecule magnets and molecular qubits. However, there have been few detailed studies of its nature. Here, we show for the first time distinct couplings of g phonons of Co(acac)(HO) (acac = acetylacetonate) and its deuterated analogs with zero-field-split, excited magnetic/spin levels (Kramers doublet (KD)) of the S = 3/2 electronic ground state. The couplings are observed as avoided crossings in magnetic-field-dependent Raman spectra with coupling constants of 1-2 cm. Far-IR spectra reveal the magnetic-dipole-allowed, inter-KD transition, shifting to higher energy with increasing field. Density functional theory calculations are used to rationalize energies and symmetries of the phonons. A vibronic coupling model, supported by electronic structure calculations, is proposed to rationalize the behavior of the coupled Raman peaks. This work spectroscopically reveals and quantitates the spin-phonon couplings in typical transition metal complexes and sheds light on the origin of the spin-phonon entanglement.
自旋-声子耦合在单分子磁体和分子量子比特中起着重要作用。然而，对其性质的详细研究却很少。在这里，我们首次展示了 Co(acac)(HO)（acac=乙酰丙酮化物）及其氘代类似物的 g 声子与零场分裂的、激发的磁/自旋能级（S=3/2 电子基态的 Kramers 双重态（KD））之间的明显耦合。这些耦合表现为磁场依赖的拉曼光谱中的回避交叉，耦合常数为 1-2 cm。远红外光谱揭示了磁偶极允许的 KD 间跃迁，随着磁场的增加，跃迁向更高的能量移动。密度泛函理论计算用于合理化声子的能量和对称性。提出了一个声子耦合模型，该模型得到电子结构计算的支持，用于合理化耦合拉曼峰的行为。这项工作通过光谱学揭示和量化了典型过渡金属配合物中的自旋-声子耦合，并阐明了自旋-声子纠缠的起源。
