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Electron dephasing in disordered metals

Peter Schwab

Institut fuer Physik, Universitaet Augsburg, D-86135 Augsburg, Germany

Peter.Schwab@Physik.Uni-Augsburg.de
Electronic quantum effects in disordered conductors are controlled by the
conduction electrons dephasing rate. It is well known that elastic scattering
does not destroy phase coherence, so it takes inelastic scattering to do that.
The resulting phase breaking rate generically vanishes when the temperature
goes to zero.

These well established theoretical results have been challenged in recent
experiments showing a saturation of the dephasing rate at low temperature [1].

Here I discuss new theoretical developments.
There have been attempts to explain the saturation of the
dephasing time from interaction with zero point motion of the
electromagnetic environment but these have been severely criticized by various
groups.
On the other hand it has been demonstrated that
a weakly temperature dependent or even temperature independent dephasing rate
is possible
in presence of ``dynamic defects'' which may be modeled
by two level systems [2,3].
It has been pointed out that the dynamics which is responsible for dephasing
is related to the low frequency conductance noise. Measuring noise and the
dephasing
rate at the same samples then provides a test for this scenario.

Furthermore the dephasing rate for the electron-electron interaction correction
to the conductivity has been calculated [4]. It has been found that
the dephasing rates for the interaction correction and for weak localization
need not
be identical, and the ratio depends on the explicit microscopic dephasing
mechanism. A saturation of the interaction correction has indeed been observed
at low
temperature in the gold wires of Ref. [1].

**References**

[1] P. Mohanty, E.M. Jariwala, R.A. Webb, Phys. Rev. Lett. 77, 3366
(1997);
Fortschr. der Physik 46, 779 (1998).

[2] Y. Imry, H. Fukuyama, and P. Schwab, preprint cond-mat/9903017, to be
published
in Europhys. Lett. (1999).

[3] A. Zawadowski, J. von Delft, D.C. Ralph, preprint cond-mat/9902176.

[4] R. Raimondi, P. Schwab, and C. Castellani, preprint cond-mat/9903146, to
be published in
Phys. Rev. B (1999).