Determination of the Phase Shifts for Interacting Electrons Connected to Reservoirs(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

概要

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We describe a formulation to deduce the phase shifts, which determine the ground-state properties of interacting quantum-dot systems with the inversion symmetry, from the fixed-point eigenvalues of the numerical renormalization group (NRG). Our approach does not assume the specific form of the Hamiltonian nor the electron-hole symmetry, and it is applicable to a wide class of quantum impurities connected to noninteracting leads. We apply the method to a triple dot which is described by a three-site Hubbard chain connected to two noninteracting leads, and calculate the dc conductance away from halffilling. The conductance shows the typical Kondo plateaus of the Unitary limit g≃2e^2/h in some regions of the onsite energy ∈_d, at which the total number of electrons N_<el> in the three dots is odd, i.e., N_<el>≃1, 3 and 5. In contrast, the conductance shows a wide minimum in the regions of ∈_d corresponding to even number of electrons N_<el>≃2 and 4. We also discuss the parallel conductance of the triple dot connected transversely to four leads, and show that it can be deduced from the two phase shifts defined in the two-lead case.
社団法人日本物理学会の論文
2005-09-15