Supersymmetric approach to Multi-electron Anderson Models

Shinji Watanabe, Hiroaki Kusunose, 渡辺 真二

Anna Kauch, Krzysztof Byczuk

P. Schlottmann, Andrei A. Zvyagin

A quantum wire of finite length L with correlated electrons coupled to a quantum dot is studied. The wire is parametrized in terms of the supersymmetric $t\ensuremath{-}J$ model and the dot is represented by an Anderson-like impurity. The model is integrable and we discuss the properties of the finite chain by solving the Bethe Ansatz equations. For a finite ring the energy spectrum is discrete and has to be obtained numerically. As a function of the coupling of the dot to the wire we discuss the ground state and low-energy excitations, the Aharonov-Bohm oscillations and the discontinuities of the magnetization of the system.

Andrei A. Zvyagin, P. Schlottmann

We study a one-dimensional n -channel highly correlated electron model (based on the supersymmetric t-J model) with a magnetic impurity of arbitrary spin S that can hybridize with up to one itinerant electron per channel. The model extends the multichannel Kondo problem to correlations in the host and to the mixed valence regime. The Bethe ansatz equations are derived and solved for the ground state and for low temperatures. We conclude that the critical non-Fermi-liquid (overscreened) behaviour cannot be reached for this interacting electron system. Possible applications of the model are discussed.

Yu Zhou, Samuel P. Bowen, Jay D. Mancini

Marco Lo Schiavo, Alfonso Romano, Canio Noce

We introduce a new measure of quantum entanglement, the orbital concurrence, designed to quantify orbital correlations in interacting multi-orbital electron systems. This quantity extends the concept of concurrence, originally developed for charge and spin degrees of freedom, to the orbital sector, providing a compact and physically transparent characterization of orbital entanglement. To test the validity and usefulness of this measure, we apply it to the single-site Anderson model, a paradigmatic and exactly solvable system that captures the essential interplay between localized correlated electrons and itinerant ones. In this framework, we derive exact, fully analytical expressions for the orbital concurrence and investigate its behavior in different regimes of interaction strength and hybridization. Our results demonstrate the diagnostic power of the proposed measure and open the way to its use in more complex multi-orbital impurities and lattice models.