Europhys. Lett, 47 (2), pp. 164-170 (1999)
Relaxation and aging in quantum spin systems
G. M. Schütz 1 and S. Trimper 2
1 Institut für Festkörperforschung,
Forschungszentrum Jülich - D-52425 Jülich, Germany
2 Fachbereich Physik, Martin-Luther-Universität - D-06099 Halle, Germany
(received 9 April 1999; accepted 4 May 1999)
PACS. 05.70Ln - Nonequilibrium and irreversible
PACS. 05.30 - Quantum statistical mechanics.
PACS. 75.40Gb - Dynamic properties (dynamic susceptibility, spin waves, spin diffusion,
dynamic scaling, etc.).
The nonthermal quantum relaxation of the magnetization under nonequilibrium initial conditions is studied for the transverse Ising chain and for the one-dimensional isotropic XY model. In the absence of a heat bath the transverse Ising system exhibits an oscillating relaxation with a decaying amplitude. At the critical transverse field some stationary properties become independent of the initial state. The isotropic XY chain with a spatially inhomogeneous initial state shows a slow, modulated algebraic decay of the magnetization. Analysis of the two-time autocorrelation function reveals the phenomenon of aging.
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