Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland.
J Phys Condens Matter. 2012 Feb 8;24(5):055303. doi: 10.1088/0953-8984/24/5/055303. Epub 2012 Jan 17.
A system of two quantum dots attached to external electrodes is considered theoretically in the orbital Kondo regime. In general, the double dot system is coupled via both Coulomb interaction and direct hopping. Moreover, the indirect hopping processes between the dots (through the leads) are also taken into account. To investigate the system's electronic properties we apply the slave-boson mean field (SBMF) technique. With the help of the SBMF approach the local density of states for both dots and the transmission (as well as linear and differential conductance) is calculated. We show that Dicke- and Fano-like line shapes may emerge in the transport characteristics of the double dot system. Moreover, we observed that these modified Kondo resonances are very susceptible to the change of the indirect coupling's strength. We have also shown that the Kondo temperature becomes suppressed with increasing asymmetry in the dot-lead couplings when there is no indirect coupling. Moreover, when the indirect coupling is turned on the Kondo temperature becomes suppressed. By allowing a relative sign of the nondiagonal elements of the coupling matrix with left and right electrodes, we extend our investigations to become more generic. Finally, we have also included the level renormalization effects due to indirect tunneling, which are mostly neglected.
理论上考虑了连接到外部电极的两个量子点的系统在轨道近藤区。一般来说，双点系统通过库仑相互作用和直接跃迁耦合。此外，还考虑了点之间的间接跃迁过程（通过引线）。为了研究系统的电子特性，我们应用了奴隶-玻色平均场（SBMF）技术。借助 SBMF 方法，计算了两个点的局域态密度和传输（以及线性和微分电导）。我们表明，双点系统的传输特性可能出现 Dicke 和 Fano 型线形状。此外，我们观察到，当间接耦合强度发生变化时，这些修正的近藤共振非常敏感。我们还表明，当没有间接耦合时，当点-引线耦合的不对称性增加时，近藤温度会受到抑制。此外，当打开间接耦合时，近藤温度会受到抑制。通过允许耦合矩阵的非对角元素与左和右电极的相对符号，我们将研究扩展到更通用的情况。最后，我们还包括了由于间接隧道而导致的能级重整化效应，这些效应大多被忽略了。
