Shot noise of Coulomb drag current

We work out a theory of shot noise in a special case. This is a noise of the Coulomb drag current excited under the ballistic transport regime in a one-dimensional nanowire by a ballistic non-Ohmic current in a nearby parallel nanowire. We predict sharp oscillation of the noise power as a function of gate voltage or the chemical potential of electrons. We also study dependence of the noise on the voltage V across the driving wire. For relatively large values of V the noise power is proportional to V^2.Comment: 9 pages, 2 figure

Theory of femtosecond photon echo decay in semiconductors

The authors investigate a mechanism responsible for the observed very short times of the photon echo decay (of the order of a few femtoseconds) in semiconductors. It is associated with the loss of phase memory as a result of interaction of the mixed state (associated with interband transitions) with an unscreened random Coulomb potential of the photocarriers or with a random static potential of the impurities. Qualitative physical consideration enabling one to visualize the process of echo decay are presented. They have introduced a new time characteristic of a system of interacting electrons. This is the time of phase breaking, {tau}{sub {var_phi}} which they calculate within the eikonal approximation using a diagrammatic technique. It is shown that {tau}{sub {var_phi}} is typically much shorter than both the period of plasma oscillations and the time of electron-electron collisions. The screening of Coulomb potential cannot build up during this time. {tau}{sub {var_phi}} is proportional to n{sup {minus}1/d} (where n is the carrier concentration, d the dimensionality of a system) which is consistent with the experimental results