Phonon-assisted decoherence in solid-state NMR

F. D. DOMÍNGUEZ; C. E. GONZÁLEZ; R. C. ZAMAR; H. H. SEGNORILE

Florianópolis

Congreso; Q-Turn: changing paradigms in quantum science; 2018

A cutting-edge subject in the research of irreversible processes is the study of the quantum dynamics of many-particle interacting systems coupled with a quantum correlated environment. In this work, we study the quantum adiabatic decoherence of a multi-spin array, coupled with an environment of harmonic phonons. We follow the basic formal guidelines of the well-known spin-boson model. However, instead of considering a set of uncoupled spins interacting individually with the boson field, the observed system in our model is a network of weakly interacting spin pairs, the bath corresponds to lattice phonons, and the system-environment interaction is generated by the variation of the dipole-dipole energy due to correlated shifts of the spin positions, produced by the phonons. We also analyzed the validity of this theoretical model by studying decoherence times in solid-state NMR experiments. The experimental response of the decoherence times to temperature, the orientation of the crystals to the external magnetic field and the rf pulse amplitudes are studied. We found that the observed attenuation of the NMR signals can be explained by two independent mechanisms: (a) the unitary evolution of the refocalization sequence used and (b) an intrinsic mechanism having the attributes of irreversible decoherence induced by the coupling with a quantum environment. The model provides insight into the microscopic irreversible spin dynamics involved in the buildup of quasiequilibrium states and in the coherence leakage during refocusing experiments in nuclear magnetic resonance of crystalline solids.