Phase lapses in transmission through interacting two-level quantum dots

Abstract

We investigate the appearance of pi lapses in the transmission phase theta of a two-level quantum dot with Coulomb interaction U. Using the numerical and functional renormalization group methods we study the entire parameter space for spin-polarized as well as spin-degenerate dots, modeled by spinless or spinful electrons, respectively. We investigate the effect of finite temperatures T. For small T and sufficiently small single-particle spacings delta of the dot levels we find pi phase lapses between two transmission peaks in an overwhelming part of the parameter space of the level-lead couplings. For large delta the appearance or not of a phase lapse between resonances depends on the relative sign of the level-lead couplings in analogy to the U=0 case. We show that this generic scenario is the same for spin-polarized and spin-degenerate dots. We emphasize that in contrast to dots with more levels, for a two-level dot with small delta and generic dot-lead couplings (that is up to cases with special symmetry) the "universal" phase lapse behavior is already established at U=0. The most important effect of the Coulomb interaction is to increase the separation of the transmission resonances. The relation of the appearance of phase lapses to the inversion of the population of the dot levels is discussed. For the spin-polarized case and low temperatures we compare our results to recent mean-field studies. For small delta correlations are found to strongly alter the mean-field picture.

submitted to NJP

References in corpus (6)

• Real-time dynamics in Quantum Impurity Systems: A Time-dependent Numerical Renormalization Group Approach
• A novel approach to transport through correlated quantum dots
• Unified description of correlations in double quantum dots
• Minimal realization of the Orbital Kondo effect in a Quantum Dot with two Leads
• Transmission phase lapses in quantum dots: the role of dot-lead coupling asymmetry
• Transmission zero in a quantum dot with strong electron-electron interaction: Perturbative conductance calculations

Cited by in corpus (6)

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• A finite-frequency functional RG approach to the single impurity Anderson model
• Supercurrent and multiple singlet-doublet phase transitions of a quantum dot Josephson junction inside an Aharonov-Bohm ring
• Transmission phase lapses in quantum dots: the role of dot-lead coupling asymmetry
• Level-occupation switching of the Quantum Dot, and phase anomalies in mesoscopic interferometry
• Transport through correlated quantum dots: An investigation using the functional renormalization group