Statistics of Current Fluctuations and Electron-Electron Interactions in Mesoscopic Coherent Conductors

We formulate a general path integral approach which describes statistics of current fluctuations in mesoscopic coherent conductors at arbitrary frequencies and in the presence of interactions. Applying this approach to the non-interacting case, we analyze the frequency dispersion of the third cumulant of the current operator ${\cal S}_3$ at frequencies well below both the inverse charge relaxation time and the inverse electron dwell time. This dispersion turns out to be important in the frequency range comparable to applied voltages. For comparatively transparent conductors it may lead to the sign change of ${\cal S}_3$. We also analyze the behavior of the second cumulant of the current operator ${\cal S}_2$ (current noise) in the presence of electron-electron interactions. In a wide range of parameters we obtain explicit universal dependencies of ${\cal S}_2$ on temperature, voltage and frequency. We demonstrate that Coulomb interaction decreases the Nyquist noise. In this case the interaction correction to the noise spectrum is governed by the combination $\sum_nT_n(T_n-1)$, where $T_n$ is the transmission of the $n$-th conducting mode. The effect of electron-electron interactions on the shot noise is more complicated. At sufficiently large voltages we recover two different interaction corrections entering with opposite signs. The net result is proportional to $\sum_nT_n(T_n-1)(1-2T_n)$, i.e. Coulomb interaction decreases the shot noise at low transmissions and increases it at high transmissions.Comment: 12 pages, 3 figures. To be published in the Proceedings of the SPIE Symposium on Fluctuations and Noise, Maspalomas, Grand Canaria, Spain (May 2004

Strong Tunneling and Coulomb Blockade in a Single-Electron Transistor

We have developed a detailed experimental study of a single-electron transistor in a strong tunneling regime. Although weakened by strong charge fluctuations, Coulomb effects were found to persist in all samples including one with the effective conductance 8 times higher than the quantum value (6.45 k$\Omega$)$^{-1}$. A good agreement between our experimental data and theoretical results for the strong tunneling limit is found. A reliable operation of transistors with conductances 3-4 times larger than the quantum value is demonstrated.Comment: revtex, 4 page

Strong Electron Tunneling through a Small Metallic Grain

Electron tunneling through mesoscopic metallic grains can be treated perturbatively only provided the tunnel junction conductances are sufficiently small. If it is not the case, fluctuations of the grain charge become strong. As a result (i) contributions of all -- including high energy -- charge states become important and (ii) excited charge states become broadened and essentially overlap. At the same time the grain charge remains discrete and the system conductance $e$-periodically depends on the gate charge. We develop a nonperturbative approach which accounts for all these features and calculate the temperature dependent conductance of the system in the strong tunneling regime at different values of the gate charge.Comment: revtex, 8 pages, 2 .ps figure

Evidence for magnetoplasmon character of the cyclotron resonance response of a two-dimensional electron gas

Experimental results on the absolute magneto-transmission of a series of high density, high mobility GaAs quantum wells are compared with the predictions of a recent magnetoplasmon theory for values of the filling factor above 2. We show that the magnetoplasmon picture can explain the non-linear features observed in the magnetic field evolution of the cyclotron resonance energies and of the absorption oscillator strength. This provides experimental evidence that inter Landau level excitations probed by infrared spectroscopy need to be considered as many body excitations in terms of magnetoplasmons: this is especially true when interpreting the oscillator strengths of the cyclotron transitions

ПРОБЛЕМИ ДУХОВНО-МОРАЛЬНОГО ВИХОВАННЯ МОЛОДІ НА ЗАСАДАХ ХРИСТИЯНСЬКОГО ВІРОВЧЕННЯ У ЗАСОБАХ МАСОВОЇ ІНФОРМАЦІЇ РІВНЕНЩИНИ. (Problems of spiritual and moral education of young people on the principles of the Christian Doctrine in the mass media of the Rivne region.)

У статті розкрито тему важливості духовно-морального виховання молоді на засадах християнського віровчення через засоби масової інформації; проаналізовано сучасний стан його здійснення в інформаційному просторі Рівненщини та подано рекомендації щодо напрямків роботи з метою поліпшення існуючої ситуації у даній сфері. (In this article we discuss the importance of educating young people on spiritual and moral principles which are based on teaching of Christianity and how it is represented in the mass media; we analyze its current situation in informational space of Rivne region and give the recommendations how to improve today's situation in this sphere.