Browsing by Subject "Mesoscopics"

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Open Access
Quantum turnstile regime of nanoelectromechanical systems
(American Physical Society, 2020) Dragomir, R.; Moldoveanu, V.; Stanciu, S.; Tanatar, Bilal
The effects of a turnstile operation on the current-induced vibron dynamics in nanoelectromechanical systems (NEMS) are analyzed in the framework of the generalized master equation. In our simulations each turnstile cycle allows the pumping of up to two interacting electrons across a biased mesoscopic subsystem which is electrostatically coupled to the vibrational mode of a nanoresonator. The time-dependent mean vibron number is very sensitive to the turnstile driving, rapidly increasing/decreasing along the charging/discharging sequences. This sequence of heating and cooling cycles experienced by the nanoresonator is due to specific vibron-assisted sequential tunneling processes along a turnstile period. At the end of each charging/discharging cycle the nanoresonator is described by a linear combination of vibron-dressed states sν associated to an electronic configuration ν. If the turnstile operation leads to complete electronic depletion the nanoresonator returns to its equilibrium position, i.e., its displacement vanishes. It turns out that a suitable bias applied on the NEMS leads to a slow but complete cooling at the end of the turnstile cycle. Our calculations show that the quantum turnstile regime switches the dynamics of the NEMS between vibron-dressed subspaces with different electronic occupation numbers. We predict that the turnstile control of the electron-vibron interaction induces measurable changes on the input and output transient currents.
Open Access
A time-dependent study of bistability in resonant tunneling structures
(1997) Keçecioğlu, Ersin
A comjDutational time-dependent study of the bistability in resonant tunneling structures including the electron-electron interactions is presented. A new computational method for the investigation of many jDarticle interacting systems for the study of quantum transport in small systems is introduced. The timedependence of the wave-function in the Schrödinger equation is studied by discretizing the energy spectrum and the time steps. A simple model for a double barrier resonant tunneling structure is introduced. The method is then applied to this simple model of double barrier resonant tunneling structure, and this geometry is investigated systematically in terms of inter-pcirticle interaction strength and number of particles. By applying the method to this simple geometry it is shown that there exists instabilities which occur a.s oscillcitions in the current-voltage characteristics of the model geometry.