Ground-state properties of a triangular triple quantum dot connected to superconducting leads

International Conference on Strongly Correlated Electron Systems 2014

Oguri, Akira^1 ; Sato, Izumi^1 ; Shimamoto, Masashi^1 ; Tanaka, Yoichi^2

Department of Physics, Osaka City University, Osaka

558-8585, Japan^1

Condensed Matter Theory Laboratory, RIKEN, Saitama

351-0198, Japan^2

关键词: Effective Hamiltonian;    Exact diagonalization;    Ground state properties;    Josephson-junction;    Numerical renormalization groups;    Parameter spaces;    Superconducting lead;    Triangular configuration;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/592/1/012143/pdf
DOI  :  10.1088/1742-6596/592/1/012143

来源: IOP

【 摘 要 】

We study ground-state properties of a triangular triple quantum dot connected to two superconducting (SC) leads. In this system orbital motion along the triangular configuration causes various types of quantum phases, such as the SU(4) Kondo state and the Nagaoka ferromagnetic mechanism, depending on the electron filling. The ground state also evolves as the Cooper pairs penetrate from the SC leads. We describe the phase diagram in a wide range of the parameter space, varying the gate voltage, the couplings between the dots and leads, and also the Josephson phase between the SC gaps. The results are obtained in the limit of large SC gap, carrying out exact diagonalization of an effective Hamiltonian. We also discuss in detail a classification of the quantum states according to the fixed point of the Wilson numerical renormalization group (NRG). Furthermore, we show that the Bogoliubov zero-energy excitation determines the ground state of a π Josephson junction at small electron fillings.