1,466 research outputs found
Quantum Environments: Spin Baths, Oscillator Baths, and applications to Quantum Magnetism
The low-energy physics of systems coupled to their surroundings is understood
by truncating to effective Hamiltonians; these tend to reduce to a few
canonical forms, involving coupling to "baths" of oscillators or spins. The
method for doing this is demonstrated using examples from magnetism,
superconductivity, and measurement theory, as is the way one then solves for
the low-energy dynamics. Finally, detailed application is given to the exciting
recent Quantum relaxation and tunneling work in naomagnets.Comment: Chapter in "Tunneling in Complex Systems" (World Sci., edited T.
Tomsovic); 97 pages. Published in June 199
Dynamics of a Pair of Interacting Spins Coupled to an Environmental Sea
We solve for the dynamics of a pair of spins, coupled to each other and also
to an environmental sea of oscillators. The environment mediates an indirect
interaction between the spins, causing both mutual coherence effects and
dissipation. This model describes a wide variety of physical systems, ranging
from 2 coupled microscopic systems (eg., magnetic impurities, bromophores,
etc), to 2 coupled macroscopic quantum systems. We obtain analytic results for
3 regimes, viz., (i) The locked regime, where the 2 spins lock together; (ii)
The correlated relaxation regime (mutually correlated incoherent relaxation);
and (iii) The mutual coherence regime, with correlated damped oscillations.
These results cover most of the parameter space of the system.Comment: 49 pages, To appear in Int J. Mod. Phys.
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