Dynamic ligand fields in qubits

Abstract

The magnetization dynamics of transition metal complexes are heavily influenced by the coupling of electron spin to vibrations (i.e., spin-phonon coupling), which greatly hinders the development of room temp. functional materials for quantum information processing. While this coupling is recognized as deriving from dynamic distortions about the first coordination sphere of the metal, a general model for understanding and quantifying ligand field contributions has not been established. Here we discuss the derivation and application of a ligand field theory model to describe the nature of spin-phonon coupling in transition metal complexes, with a specific emphasis on quantum bits (qubits). We show the nature of the coupling term for a given vibrational mode and transition metal is heavily dependent on dynamical contributions from ligand field excited state energies and relativistic nephelauxetic contributions reflecting the covalency of ligand-metal bonds. While providing a fundamental framework and means to benchmark the coherence lifetimes of current qubits, the model and methodol. described herein can be used to screen any qubit candidate and guide the discovery of room temp. coherent materials for quantum information processes. Time permitting, the extension of this model to the spin state dynamics of S > 1/2 complexes will also be discussed.

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