Magnetic Field Dependent Kondo Transport through Double Quantum Dots System

The Kondo transport associated with the magnetic field in parallel-coupled double quantum dots (PDQDs) is theoretically investigated using the hierarchical-equation-of-motion approach (HEOM). In this system, the interdot tunneling induces an effective antiferromagnetic interaction; thus, its ground state is an orbital singlet associated with approximately zero differential conductance. When an appropriate large magnetic field is applied, the two spins of the two dots have a possibility with a parallel arrangement, and thus the singlet and one of the triplets are degenerated. At the degenerate point, a distinct zero-energy resonance peak appears, associated with significant differential conductance. The Kondo scale behavior at the degenerate point and the total and spin resolved spectral functions around the degenerate point are examined. The results confirm the spin-1/2 Kondo resonance near the singlet-triplet transition point. The differential conductance phase diagram, as well as thermoelectric transport, is also quantitatively presented.