Friday, October 6th, 2006

 

Prof. Vladimir Gasparian, California State University, Bakersfield

" Pumping in 1D Kronig-Penney models: Without and with effects of electron-electron interaction "

2:00 pm in room P-148

We consider adiabatic charge transport through 1D open chain for two delta-like pumping sources with and without taking into account e-e interaction (weak). We obtain explicitly the charge Q pumped within a period. This charge turns out to be proportional to the conductance G0 of the system in between two pumping sources. For weak pumping perturbation the charge Q is proportional to the area of the contour in parametric space and to sin(phi), where phi is the phase difference of the oscillations of the two parameters. There is an intermediate regime, where Q is proportional to the length of the contour and to sin(phi)/2. For large pumping strength the charge decreases as (nu sin(phi))^-3. In the case when the conductance of the system is close to its maximum G₀=1, in a finite range of pumping potentials the charge is almost quantized, gets closer and closer to the unit charge as we increase the constant term of the oscillating potentials. Weak e-e interaction effects depress the intermediate regime and the pumping current no longer proportional to the length of the contour but still can be quantized at low temperatures.