September, 27 (2006) at 4pm

Simon E. Nigg
University of Geneva

We consider a mesoscopic capacitor, one plate of which is formed by a quantum dot (QD) and the other consists of a macroscopic gate electrode. Closing the circuit by contacting the QD to an electron reservoir via a tunable quantum point contact (QPC) gives rise to the so called charge relaxation resistance. This resistance, together with the electro-chemical capacitance, determines the charge relaxation time of the system in close analogy to the classical case. However, the quantum coherent nature of electron transport through a mesoscopic structure strongly affects the charge relaxation process. It has been predicted [1] and recently verified experimentally [2], that at very low temperatures and in the case where only a single mode is transmitted through the QPC, the charge relaxation resistance is equal to half a resistance quantum h/2e^2 and does not depend on the transmission probability of the mode. I will discuss a model for the electrochemical capacitance and the charge relaxation resistance, which takes into account self-consistently both the electron-electron interaction leading to charge quantization in the dot and the screening due to the presence of external gates [3, 4]. In particular, I will present numerical results on the effects of interaction on the electrochemical capacitance as well as on the temperature and magnetic field dependence of the charge relaxation resistance. [1] M. Buttiker, H. Thomas, and A. Preetre, Phys. Lett. A 180, 364 (1993). [2] J. Gabelli, J. M. Berroir, G. Feve, B. Placais, Y. Jin, B. Etienne and D. C. Glattli, Science 313, 499-502 (2006). [3] S. E. Nigg, R. Lopez and M. Buttiker, cond-mat/0606603. [4] M. Buttiker and S. E. Nigg, cond-mat/0608417.