Survival Probability and Multiple Quantum Coherence in 1d spin chain

E. RUFEIL FIORI; F. OLIVA; P. R. LEVSTEIN; H. M. PASTAWSKI

Córdoba

Congreso; Magnetic Resonance in a Cordubensis Perspective; 2006

Using nuclear magnetic resonance techniques, one can generate effective Hamiltonians that mixes subspaces with different spin projection creating many-body superposition states: the multiple quantum coherences. These states can be probed through a bidimensional technique that allows one to follow the superposition weights as they are created. In this work we address effects that some spins, considered as ?environment?, has on the excitations of other spins, considers as the ?system?. To simplify the treatment we consider a single spin excitation which is weakly coupled to an environment whose dynamics can be solved within a Hamiltonian model. Various works showed that the exponential decay has superimposed beats and does not hold for very short and very long times, compared with the lifetime of the system. We presented a model describing the evolution of a surface excitation in a semi-infinite spin chain, a model that is solved analytically and susceptible for an experimental test. Here, we present a general analysis showing the quantum nature of the deviations from the Fermi Golden Rule. We identify three time regimes in the decay of the local polarization.