The evolution of local spin polarization in finite systems involves interference phenomena that give rise to { \bf quantum dynamical echoes }and non-ergodic behavior. We predict the conditions to observe these echoes by exploiting the NMR sequences devised by Zhang et al. [Phys. Rev. Lett. { \bf % 69}, 2149 (1992)], which uses a rare $^{ 13}$C as { \bf local probe }for a dipolar coupled $^1$H spin system. The non-ideality of this probe when testing mesoscopic systems is carefully analyzed revealing the origin of various striking experimental features.
Categories: cond-mat