Effects of orbital splitting and three-body correlations in the low-energy transport through SU(4) quantum dots

In multi-orbital quantum dot systems, such as carbon nanotube quantum dots, various Kondo effects arise due to orbital splitting, and the behavior of the linear conductance at low temperatures has been precisely studied using the numerical renormalization group (NRG) approach [1]. Recent theoretical developments have revealed that the next-to-leading order term of transport coefficients, such as the nonlinear current proportional to the cubic power of the bias voltage V, is systematically influenced by the three-body correlations between localized electrons in the low-energy Fermi liquid regime [2]. However, previous studies on three-body correlations have primarily focused on systems exhibiting SU(N) symmetry, in which the discrete energy level of quantum dots has N-fold degeneracy. In this study, we extend the microscopic formulation of higher-order Fermi liquid corrections to systems in which the degeneracy is lifted by external fields or other intrinsic potentials. Using the NRG approach, we investigate the behavior of the next-to-leading order terms of the transport coefficients, such as nonlinear shot noise and thermal conductance, over a wide region of the electron filling of impurity levels of N=4 Anderson model. We also discuss Kondo scaling behaviors which occur at 1/4-filling and 1/2-filling at small level-splittings.

[1] W. Izumida, O. Sakai, and Y. Shimizu, J. Phys. Soc. Jpn. 67, 2444 (1998).

[2] Y. Teratani, K. Tsutsumi, K. Motoyama, R. Sakano, and A. Oguri, PRB 110, 035308 (2024).