Excited-State Dynamics and Optically Detected Magnetic Resonance of Solid-State Spin Defects from First-Principles

Optically detected magnetic resonance (ODMR) is an efficient and reliable method that enables initialization and readout of spin states through spin-photon interface. In general, high quantum efficiency and large spin-dependent photoluminescence (PL) contrast are desired for reliable spin information readout. However, first-principle tools for modeling ODMR contrast under external fields are not yet available, due to the complex dynamical processes, including optical excitation, and radiative and nonradiative excited-state relaxations. Therefore, we developed first-principles spin-dependent ODMR simulation method through solving kinetic master equation, with radiative, internal conversion and intersystem crossing (ISC) rates computed from first-principles, under microwave and magnetic fields. We show the importance of correct description of multireference electronic states for accurately predicting the excitation energy, spin-orbit coupling, and ISC by comparing CASSCF, TDDFT and DFT methods. We then underscore the importance of dynamical and pseudo Jahn-Teller effects for the spin-orbit coupling, a key factor determining ISC rates and ODMR contrast. Our first-principle method provides good agreement with the experimental ODMR contrast under magnetic field for NV center in diamond. Our work clarifies the important excited-state relaxation mechanisms determining ODMR contrast and provides a predictive computational tool for new solid-state spin defects with high readout fidelity and efficiency from first-principles.