QUANTUM DYNAMICAL ECHOES IN THE SPIN-DIFFUSION IN MESOSCOPIC SYSTEMS

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