چكيده به لاتين
The generation of a net charge current in the absence of explicit bias, a phenomenon known as pumping, is being considered to study the electronic transport. After the first theoretical proposal of charge transfer via pumping by Thouless, the technique was analyzed in detail by studying several mesoscopic models and also shown to work in real experimental settings with periodic time dependent voltages applied to di erent systems. In this document, the properties of non-equilibrium zero-bias currents produced by two external out-of-phase time-dependent harmonic potentials through systems with varying dimensionality, are analyzed. A non-equilibrium Keldysh formalism, based on Green’s functions, is used to solve tight-binding models for one-, quasi-one (ribbons) and two-dimensional systems with square and honeycomb lattice connectivity. A full description of DC currents and current spectral functions has been carried out for di erent model parameter values describing adiabatic, non-adiabatic, linear and non-linear regimes. Transmission probability and charge current have been calculated and compared for both a symmetrical and asymmetrical quantum wire. Results suggest that the transmission in symmetrical quantum wire has no band gap but when two different kinds of atoms is used in the wire, appearance of a gap is observed. Furthermore, pumping current for both adiabatic and non-adiabatic states is calculated. It can be seen that in the adiabatic state, the current oscillates like Sinus whereas in the non-adiabatic state this behavior is not observed and the pumped current varies depending on the distance between energy states. After investigation of current in the pseudo-one-dimensional systems, it was shown that the pumped current in comparison with one-dimensional systems in non-adiabatic states, has negligible difference. Other investigations show that the pumped current in two-dimensional systems increase with increasing transmission channels
