Quantum Noise Measurement of a Carbon Nanotube Quantum Dot in the Kondo Regime

TL;DR

This study measures the high-frequency emission noise of a carbon nanotube quantum dot in the Kondo regime, revealing frequency-dependent singularities that align with theoretical predictions, thus providing a new tool for exploring many-body dynamics.

Contribution

First measurement of high-frequency emission noise in a Kondo regime quantum dot using an on-chip resonant circuit and superconducting detector.

Findings

Identified a Kondo-related singularity at specific voltages and frequencies.

Observed a strong reduction of the singularity at higher frequencies.

Results agree with theoretical models of non-equilibrium Kondo physics.

Abstract

The current emission noise of a carbon nanotube quantum dot in the Kondo regime is measured at frequencies $\nu$ of the order or higher than the frequency associated with the Kondo effect $k_B T_K/h$, with $T_K$ the Kondo temperature. The carbon nanotube is coupled via an on-chip resonant circuit to a quantum noise detector, a superconductor-insulator-superconductor junction. We find for $h \nu \approx k_B T_K$ a Kondo effect related singularity at a voltage bias $eV \approx h \nu $, and a strong reduction of this singularity for $h \nu \approx 3 k_B T_K$, in good agreement with theory. Our experiment constitutes a new original tool for the investigation of the non-equilibrium dynamics of many-body phenomena in nanoscale devices.