Effects of three-body correlations on nonlinear current noise through an <i>N</i>-level Anderson impurity: NRG and large <i>N</i> studies

We study nonlinear transport through an N-level Anderson impurity with finite Coulomb interactions U at low bias voltages eV, using a Fermi-liquid theory which has recently been extended to arbitrary cases of electron fillings N_d [1,2]. The nonlinear current and noise up to order of (eV)³ are determined not only by phase shifts and charge and spin static susceptibilities but also three-body correlations between impurity electrons. We calculate these parameters up to N=8 by two methods: numerical renormalization group(NRG) and 1/(N-1) expansion[3]. The latter one is a large N theory which keeps (N-1)U constant. For strong interactions U, NRG results show that the three-body contributions can be described by a single parameter over a range of 1≤N_d≤N-1 [4,5]. We also find that the three-body correlations significantly affect the noise, especially near N_d=1 and N_d=N-1. Furthermore, the results of two methods agree well with each other already at N=8 for weak interactions.

[1] A. Oguri and A. C. Hewson, Phys. Rev. B 97, 035435 (2018).
[2] C. Mora, and et al , Phys. Rev. B 92, 075120 (2015).
[3] A. Oguri, Phys. Rev. B 85, 155404 (2012).
[4] Y. Teratani, and et al, Phys. Rev. B 102, 165106 (2020).
[5] Y. Teratani, R. Sakano, and A. Oguri, Phys. Rev. Lett. (2020), (manuscript accepted).