Study on the Kondo effect in the tunneling phenomena through a quantum dot

We review our recent studies on the Kondo effect in the tunneling phenomena through quantum dot systems. Numerical methods to calculate reliable tunneling conductance are developed. In the first place, a case in which electrons of odd number occupy the dot is studied, and experimental results are analyzed based on the calculated result. Tunneling anomaly in the even-number-electron occupation case, which is recently observed in experiment and is ascribed to the Kondo effect in the spin singlet-triplet cross over transition region, is also examined theoretically.Comment: 9 pages, 5 figures, Proceedings of the 2nd Hiroshima Workshop--Transport and Thermal Properties of Advanced Materials--, Hiroshima, Japan, August 16-19, 200

Transmission probability through small interacting systems: application to a series of quantum dots

We apply a theory for the transmission probability of small interacting systems, which was formulated based on the Kubo formalism in our previous study, to a series of quantum dots described by the N-impurity Anderson model. In this report, we present the transmission pobability for the system of N=2 calculated using the order $U^2$ self-energy and vertex corrections. Particularly, we examine the features in the two typical parameter regions, $t\Gamma$, where the Kondo effect or the inter-dot correlation dominates. Here, $t$ is the inter-dot transfer and $\Gamma$ is the level broadening caused by the coupling with the noninteracting leads.Comment: 2 pages, 2 figures: proccedings of LT23 (Hiroshima, August, 2002

Onsager coefficients of a finite-time Carnot cycle

We study a finite-time Carnot cycle of a weakly interacting gas which we can regard as a nearly ideal gas in the limit of $T_\mathrm{h}-T_\mathrm{c}\to 0$ where $T_\mathrm{h}$ and $T_\mathrm{c}$ are the temperatures of the hot and cold heat reservoirs, respectively. In this limit, we can assume that the cycle is working in the linear-response regime and can calculate the Onsager coefficients of this cycle analytically using the elementary molecular kinetic theory. We reveal that these Onsager coefficients satisfy the so-called tight-coupling condition and this fact explains why the efficiency at the maximal power $\eta_\mathrm{max}$ of this cycle can attain the Curzon-Ahlborn efficiency from the viewpoint of the linear-response theory