Screened spin−1 and −1/2 Kondo effect in a triangular quantum dot system with interdot Coulomb repulsion. (March 2017)

• Record Type: Journal Article
• Authors: Xiong, Yong-Chen; Wang, Wei-Zhong; Luo, Shi-Jun; Yang, Jun-Tao; Huang, Hai-Ming
• Is Part Of: Superlattices and microstructures. Volume 103(2017)
• Page Start: 180
• Page End: 189
• Publication Date: 2017-03
• Subjects: Triangular quantum dot -- Kondo effect -- Quantum phase transition -- Interdot Coulomb repulsion; Superlattices as materials -- Periodicals; Microstructure -- Periodicals; Semiconductors -- Periodicals; Superréseaux -- Périodiques; Microstructure (Physique) -- Périodiques; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.spmi.2017.01.038
• Languages: English
• ISSNs: 0749-6036

Abstract

Abstract: By means of the numerical renormalization group (NRG) technique, we study the low temperature transport property and the phase transition for a triangular triple quantum dot system, including two centered dots (dot 1 and 2) and one side dot (dot 3). We focus on the effect of interdot repulsion V between two centered dots in a wide range of the interdot hopping t ij ( i, j = 1, 2, 3). When the hoppings between the centered dot and the side dot are symmetric, i.e., t 13 = t 23, and that between two centered dots t 12 is small, two centered dots form a spin triplet when V is absent, and a totally screened spin−1 Kondo effect is observed. In this case, one has a spin 1 that is partially screened by the leads as in the usual spin−1 Kondo model, and the remaining spin 1/2 degree of freedom forms a singlet with the side dot. As V is large enough, one of the centered dots is singly occupied, while the other one is empty. The spin−1/2 Kondo effect is found when t 13 is small. For large t 12, two centered dots form a spin singlet when V = 0, leading to zero conductance. As V is large enough, the spin−1/2 Kondo effect is recovered in the case of small t 13 . For asymmetric t 13 ≠ t 23 and small t 12, a crossover is found as V increases in comparison with a first order quantum phase transition for the symmetric case. In the regime of large V, the spin−1/2 Kondo effect could also be found when both t 13 and t 23 are small. We demonstrate the present model is similar to the side-coupled double dot system in some appropriate regimes, and it appears as a possible realization of side-controllable molecular electronics and spintronics devices. Highlights: The effect of interdot Coulomb repulsion on the Kondo effect in a triangular triple dot system is discussed. A totally screened spin-1 Kondo effect is revealed. A wealthy of quantum phase transitions are shown. Our results appear as a possible realization of side-controllable molecular electronics and spintronics devices.