Enhanced shot noise of multiple Andreev reflections in a carbon nanotube quantum dot in SU(2) and SU(4) Kondo regimes

TL;DR

This study investigates how Kondo correlations influence shot noise in a carbon nanotube quantum dot with superconducting contacts, revealing enhanced noise levels linked to multiple Andreev reflections and Kondo effects in different regimes.

Contribution

It demonstrates the significant enhancement of shot noise due to Kondo effects in SU(2) and SU(4) regimes, exceeding existing theoretical predictions.

Findings

Shot noise is enhanced in superconducting state.

Divergence of Fano factor is more pronounced in SU(4) regime.

Kondo effect strongly influences multiple Andreev reflections.

Abstract

The sensitivity of shot noise to the interplay between Kondo correlations and superconductivity is investigated in a carbon nanotube quantum dot connected to superconducting electrodes. Depending on the gate voltage, the SU(2) and SU(4) Kondo unitary regimes can be clearly identified. We observe enhancement of the shot noise via the Fano factor in the superconducting state. Its divergence at low bias voltage, which is more pronounced in the SU(4) regime than in the SU(2) one, is larger than what is expected from proliferation of multiple Andreev reflections predicted by the existing theories. Our result suggests that Kondo effect is responsible for this strong enhancement.