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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