Quantum criticality and non-Fermi-liquid behavior in a two-level two-lead quantum dot

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Original languageEnglish
Article number45106
Journal / PublicationPhysical Review B - Condensed Matter and Materials Physics
Issue number4
Publication statusPublished - 5 Jan 2010
Externally publishedYes


Analytical and continuous-time quantum Monte Carlo methods are used to investigate the possibility of occupation switching and quantum criticality in a model of two quantum impurities coupled to two leads. A general discussion of potential occupancy-switching-related quantum critical points is given, and a detailed analysis is made of a specific model which has been recently discussed. For spinless electrons, no phase transition is found. For electrons with spin, a critical value of the interaction strength separates a weak-coupling regime in which all properties vary smoothly with parameters from a strong-coupling phase in which occupation numbers vary discontinuously as level energies are changed. The discontinuity point is characterized by non-Fermi-liquid behavior. Results for self-energies and correlation functions are given. Phase diagrams are presented. © 2010 The American Physical Society.