Survival Probability and Multiple Quantum Coherence in 1d spin chain

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

Córdoba, Argentina

Jornada; Magnetic Resonance in a Cordubensis Perspective; 2006

LANAIS-CONICET, FaMAF-UNC

Nanosystems are never isolated, but they interact with the macroscopic

world. In consequence the excitations have a survival probability P00(t)

which typically decay according to the Fermi Golden Rule. However, this

approximation neglects memory effects in the environment, which could be

relevant. In this work we address effects that an electrode, considered as

"environment", has on the excitations of a quantum dot. To simplify the

treatment we consider a single state of the dot which is weakly coupled to

an environment whose dynamics can be solved within a Hamiltonian model.

  Various works on models for nuclei, composite particles [1] and

excited atoms in a free electromagnetic field [2], 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. In Ref. [3]

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, the validity of the Markovian

approximation and memory effects of the environment surrounding the

nanodevices.

 [1] G. García Calderón, J. Mateos, M. Moshinsky, PRL 74, 337 (1995).

 [2] P. Facchi, S. Pascazio, Phys. A 271, 133 (1999).

 [3] E. Rufeil Fiori, H. M. Pastawski, Chem. Phys. Lett. 420, 35 (2006),

quant-ph/0511176.