Study On The Transport And Photoelectric Characteristics Of New Eletronic System

This paper mainly studies the following three aspects:1)Firstly,In this work,we developed a theoretical approach to evaluate the low temperature electronic and transport properties of n-type Na3Bi semi-metal.The elec?tronic band structure,the Fermi energy,the electronic screening length induced by electron-electron interaction,the electron-impurity scattering,and the electron quan-tum and transport mobilities were examined.The main onclusions from this study are summarized as follows:The simplified k · p Hamiltonian can be reliably employed as a basis for study-ing the electronic and transport properties of Na3Bi.From the calculated electronic band structure and the Fermi energy,we discussed why the anomalous effect induced by the Berry curvature in the electronic energy band can be observed experimentally in magneto-transport experiments both in the low-and high-density samples.By tak-ing into account of electronic screening induced by electron-electron interaction and electron-impurity scattering,we calculated the quantum and transport mobilities in Na3Bi as the function of electron density for different impurity concentrations.The quantum and transport mobilities obtained from this study agree both qualitatively and quanti-tatively with those measured experimentally by Xiong et al.The electron mobilities along different crystal directions exhibit large anisotropy.The most significant conclu-sion we draw from this study is that over for high density Na3Bi samples with electron density Ne 1019cm3,the Fermi level is still not too far away from the Dirac points and from the top of the Berry curvature.Therefore,the electronic transport in high density Na3Bi samples can still exhibit the features of a 3D Dirac electronic system.We hope the results and discussions presented in this work can be helpful for the understanding of some of the basic electronic and transport properties of newly developed 3D Dirac electronic systems.2)Secondly,we present a theoretical study to evaluate the optical conductivity of an electron gas in the presence of pulsed terahertz(THz)radiation field.Applying a very simple Drude like approach,we calculate the transit current for an electron gas driven by a pulsed light field.By taking three types of the pulsed radiation fields,we proof analytically or numerically that although the corresponding transit current de-pends on the shape of the radiation field,the optical conductivity in frequency-domain is independent upon the profile of the pulsed light field when optical conductivity in frequency-domain is obtained by Fourier transformation of both the pulsed radiation field and the transit current.Thus,the obe described by the well known Drude formula even in the presence of the pulsed THz ptical conductivity in frequency-domain can field.This finding can be applied for experimental measurement of the real and imagi-nary parts of optical conductivity in electronic and opto-electronic materials using THz time-domain spectroscopy(TDS).3)Thirdly,we present a theoretical study on how many-body effect,especially the exchange interaction,can affect the spin-splitting of A n-type monolayer MoS2 in presence of proximity induced interactions.The standard Hartree-Fock approximation and Green's function approach are employed to calculatte self-energy induced by e-e interaction and energy spectrum induced self-energy.We find that although the Hartree interaction affects rather weakly the self-energy of a quasi-particle,the presence of the exchange(Fock)interaction can significantly enchance the spin-splitting of the conduc-tion band.In attention,due to vally splitting in K and K' vally,the self-energy have a little diffierences between two vallys.As a result,a large gap at spin-split state s and s'can be induced e-e interaction via Coulomb interaction.