Microscopic feedback and nonlinear nuclear spin dynamics in driven NV center ensembles

Nitrogen vacancy (NV) centers in diamond are a key platform for solid-state quantum technologies and precision sensing. In dense ensembles the surrounding nuclear and electronic spin environment cannot be treated as a purely passive noise source: the driven NV spins polarize their bath, and the resulting Overhauser field feeds back on the NV dynamics. Starting from the spin-1 NV Hamiltonian with hyperfine couplings, we use a Schrieffer–Wolff transformation to derive drive- and detuning-dependent nuclear flip rates near Hartmann–Hahn and level-anticrossing conditions. Combining these rates with optical Bloch steady states for the NV spin, we obtain closed mean-field equations for the nuclear polarization and electronic inversion. Linear stability analysis yields a dimensionless feedback gain that delineates regimes where the weakly polarized bath is stable and where it self-organizes into strongly polarized states. Within this framework we compute detuning- and drive-dependent nuclear polarization, ODMR linewidths and Hahn-echo coherence times, and construct a stability map in the drive–detuning plane that identifies feedback-active regions with substantial linewidth narrowing and T2 enhancement accessible to current NV-ensemble experiments.