Singlet-Triplet Transition in lateral Quantum Dots: A Numerical Renormalization Group Study

TL;DR

This study uses numerical renormalization group techniques to analyze electron transport through a lateral quantum dot near a singlet-triplet spin transition, revealing conductance behaviors influenced by magnetic fields.

Contribution

It provides a detailed numerical analysis of conductance near the singlet-triplet transition, connecting theoretical predictions with experimental observations.

Findings

Conductance peaks at the singlet-triplet transition.

Magnetic field causes non-monotonic conductance changes.

Reduced low-energy transport near the transition.

Abstract

We discuss transport through a lateral quantum dot in the vicinity of a singlet-triplet spin transition in its ground state. Extracting the scattering phase shifts from the numerical renormalization group spectra, we determine the linear conductance at zero temperature as a function of a Zeeman field and the splitting of the singlet and triplet states. We find reduced low-energy transport, and a non-monotonic magnetic field dependence both in the singlet and the triplet regime. For a generic set of dot parameters and no Zeeman splitting, the singlet-triplet transition may be identified with the conductance maximum. The conductance is least sensitive to the magnetic field in the region of the transition, where it decreases upon application of a magnetic field. Our results are in good agreement with recent experimental data.