Condensed Matter Physics Seminar
Thursday, October 1, 1998, 3 p.m.
Physics Building, Room 1402
Quantal Brownian Motion - Dephasing and Dissipation
Doron Cohen
(Lyman Laboratory of Physics, Harvard University)
Abstract: Quantal Brownian motion in d dimensions is analyzed.
At high temperatures the propagator exhibits a Markovian property leading
to an equivalent Master equation. Unlike the case of the Zwanzig-Caldeira-Leggett
model, genuine quantum mechanical effects manifest themselves due to the
disordered nature of the environment. Using Wigner picture of the dynamics
we distinguish between two different mechanisms for destruction of coherence:
scattering perturbative mechanism and smearing non-perturbative mechanism.
The analysis of dephasing is extended to the low temperature regime by
using a semiclassical picture. We distinguish the contribution of zero
point fluctuations (ZPF) from the thermal noise contribution. The limitations
of the semiclassical approach are studied and the required modifications
are proposed. In particular it is argued that the ZPF contribution becomes
irrelevant for thermal motion.
Host: Richard Prange
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