Study On Shot Noise In Triple-barrier Heterostructure And Confined Quantum Waveguide System

Shot noise in mesoscopic conductor is a very active field.In mesoscopic conductors, shot noise can provide an efficient tool to detect some additional informations.In this work, by using the scattering theory about shot noise in mesoscopic conductors,we studied the properties of shot noise in triple-barrier semiconductor heterostructures,and electron transport through a ballistic quantum wire structure with local Rashba spin-orbit interaction.The main results obtained in this paper are listed below:(1)We show that at zero temperature and zero frequency for a symmetric GaAs/Al_xGa_1-xAs triple-barrier structure,the results of the transmission cofficient as a function of the electron energy for four different values of the applied electric field E and the transmission cofficient and noise potential as function of the external electric field E for different values of the electron energy.We found that when the transmission cofficient as function of the energy variations with different applied bias,all resonant spectra are split into doublets.As the bias voltage is increased,the resonant state is weakened,so that the peak value of the corresponding transmission spectrum is decreased,and the distance between two peaks in the doublets will become larger.When the applied bias arrived at 0.25V,the resonant spectra could not be split into doublets.At the same time,using the transmission probability with different electron energies,we calculate the noise potential as function of the applied bias.If the electron energies are the transmission peak values of the resonant spectra with different applied bias 0.0V,0.05V,0.10V or 0.25V,when the electron energy is on the small side,two peaks are observed in transmission cofficient.As the electron energy is increased,there will be only one peak in transmission cofficient.When the value of the applied bias is away from 0.0V,and the transmission probability is equal to 1/2,there will be one peak in noise potential,when the transmission probability is larger than 1/2,a remarkable suppression are observed in the noise potential.When the value of the applied bias is close to 0.0V,no matter what the transmission probability is,the noise potential was suppressed completely. (2)Using the method of scattering approach about shot noise in the two-terminal conductor,we present a theoretical study on shot noise in a ballistic quantum wire with the local Rashba-type spin-orbit interaction(SOI).The presence of Rashba SOI make it possible to produce partial transmission through a ballistic quantum conductor,which give rise to the occurrence of pure Rashba-induced shot noise.It is also found that shot noise is completely suppressed in the conductance plateaus since electrons can go through the quantum conductor without any scattering.With the tuning of Fermi energy and the strength of Rashba SOI,we achieve the obvious signal of Rashba-induced shot noise,which can be utilized to measure the strength of SOI by means of shot noise.