Magnetic field effects on the finite-frequency noise and ac conductance of a Kondo quantum dot out of equilibrium

TL;DR

This paper provides an analytic theoretical analysis of how magnetic fields influence the finite-frequency noise and ac conductance in a Kondo quantum dot out of equilibrium, revealing resonance broadening and singular features.

Contribution

It introduces a real-time renormalization group approach to analyze magnetic field effects on noise and conductance in Kondo quantum dots, including predictions for finite magnetic fields.

Findings

Resonance line shapes are broadened by transverse spin relaxation.

Finite field noise involves both longitudinal and transverse relaxation rates.

Predictions include sharp kinks and singular derivatives in noise at finite magnetic field.

Abstract

We present analytic results for the finite-frequency current noise and the nonequilibrium ac conductance for a Kondo quantum dot in presence of a magnetic field. Using the real-time renormalization group method, we determine the line shape close to resonances and show that while all resonances in the ac conductance are broadened by the transverse spin relaxation rate, the noise at finite field additionally involves the longitudinal rate as well as sharp kinks resulting in singular derivatives. Our results provide a consistent theoretical description of recent experimental data for the emission noise at zero magnetic field, and we propose the extension to finite field for which we present a detailed prediction.