Thermal And Electric Transport Properties Of Strong Correlated Low Dimensional System

Recently, transistors of large scale integrated circuit are getting smaller andsmaller. Meanwhile, quantum dot system is a good example of strong correlatedsystem, it is a good way to study the nature of strong correlated system throughquantum dot system, so it’s a good and very important topic in condensed mattertheory. With the help of Green function methed, the thermoelectric transportproperties and electric transport properties have been investigated.The thermoelectric transport properties of the Luttinger liquid coupled to thequantum dot by tunnel junctions is investgated. A general thermopower expression isderived by using nonequilibrium Green function method. At low temperature thethermopower is of linear temperature dependence and conductance is of atemperature-dependent power-law behavior. There is a peak in the curve of thethermopower vs. gate voltage. Intralead electron interaction enhances thermopower atlow temperatures and the large slope is interpreted as a character of the Luttingerliquid.The density of states of a quantum dot weakly coupled to Luttinger liquid leadsin the Kondo regime is investigated by use of the equation-of-motion technique of thenonequilibrium Green functions. At zero temperature, the Kondo peak in DOS issuppressed by the intralead interaction. When the LL interaction parameter K is about0.77, a moderately strong interaction, the Kondo peak disappears and then a dipdevelops, a signature of the intermediate two-channel Kondo physics. This shows thatthe condition for the2CK to occur ever addressed is not necessary. Applying a fnitevoltage bias splits the dip in the DOS. Each split dip is located at the chemicalpotential of a LL lead. This again appears the stabilized2CK physics for moderatelystrong interaction K <1.For the system of a quantum dot weakly coupled to Luttinger liquid leads withdot-lead interaction, a general formula of current is derived by applying the canonicaltransformation and the nonequilibrium Green function technique. At low temperatureand weak intralead interaction, the current exhibits stair case behavior with theCoulombic dot-lead interaction. When temperature or the intralead interactionincreases, the steps are rounded. For a weak or moderately strong interaction thedifferential conductance as a function of bias voltage demonstrates resonant behavior.The dot-lead exchange scattering processes can dominate electron transport for acertain region of interaction strength. This result implies the possibility of controllingthe differential conductance of the transistor by tuning the Coulombic dot-leadcoupling.