Quantum theory of nuclear spin dynamics in diamond nitrogen-vacancy   center
  We develop a quantum theory for a variety of nuclear spin dynamics such as dephasing, relaxation, squeezing, and narrowing due to the hyperfine interaction with a generic, dissipative electronic system. The first-order result of our theory reproduces and generalizes the nonlinear Hamiltonian for nuclear spin squeezing [M. S. Rudner, Phys. Rev. Lett. 107, 206806 (2011)]. The second-order result of our theory provides a good explanation to the experimentally observed $^{13}$C nuclear spin bath narrowing in diamond nitrogen-vacancy center [E. Togan, Nature 478, 497 (2011) 
Ping Wang, Jiangfeng Du, and Wen Yang
quant-ph cond-mat.mes-hall