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arXiv:cond-mat/0108359 · Physical Review Letters

Quantum Phase Transition in a Multilevel Dot

Walter Hofstetter, Herbert Schoeller

Published Dec 19, 2001• 150 citations
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Abstract

We discuss electronic transport through a lateral quantum dot close to the singlet-triplet degeneracy in the case of a single conduction channel per lead. By applying the numerical renormalization group, we obtain rigorous results for the linear conductance and the density of states. A new quantum phase transition of the Kosterlitz-Thouless-type is found, with an exponentially small energy scale T(*) close to the degeneracy point. Below T(*), the conductance is strongly suppressed, corresponding to a universal dip in the density of states. This explains recent transport measurements.

DOI
10.1103/physrevlett.88.016803

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We present a functional renormalization group approach to the zero bias transport properties of a quantum dot with two different orbitals and in the presence of Hund's coupling. Tuning the energy separation of the orbital states, the quantum dot can be driven through a singlet-triplet transition. Our approach, based on the approach by Karrasch et al (2006 Phys. Rev. B 73 235337), which we apply to spin-dependent interactions, recovers the key characteristics of the quantum dot transport properties with very little numerical effort. We present results on the conductance in the vicinity of the transition and compare our results both with previous numerical renormalization group results and with predictions of the perturbative renormalization group.
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