Nonequilibrium Keldysh formalism for interacting leads鈥擜pplication to quantum dot transport driven by spin bias
- 作者：Yuan Li
- 关键词：Kondo effect ; Spin transport ; Differential conductance
- 刊名：Annals of Physics
- 出版年：2012
- 期刊代码：63_00034916
- 类别：mt
- 出版时间：June, 2012
- 卷：327
- 期：6
- 页码：1484-1493
- 文件大小：384 K
摘要
The conductance through a mesoscopic system of interacting electrons coupled to two adjacent leads is conventionally derived via the Keldysh nonequilibrium Green鈥檚 function technique, in the limit of noninteracting leads [Y.聽Meir, N.S.聽Wingreen, Phys. Rev. Lett. 68 (1992) 2512]. We extend the standard formalism to cater for a quantum dot system with Coulombic interactions between the quantum dot and the leads. The general current expression is obtained by considering the equation of motion of the time-ordered Green鈥檚 function of the system. The nonequilibrium effects of the interacting leads are then incorporated by determining the contour-ordered Green鈥檚 function over the Keldysh loop and applying Langreth鈥檚 theorem. The dot-lead interactions significantly increase the height of the Kondo peaks in density of states of the quantum dot. This translates into two Kondo peaks in the spin differential conductance when the magnitude of the spin bias equals that of the Zeeman splitting. There also exists a plateau in the charge differential conductance due to the combined effect of spin bias and the Zeeman splitting. The low-bias conductance plateau with sharp edges is also a characteristic of the Kondo effect. The conductance plateau disappears for the case of asymmetric dot-lead interaction.