Noise of a chargeless Fermi liquid

TL;DR

This paper develops a Fermi liquid theory for a superconductor-quantum dot-normal metal junction near a parity transition, revealing a hidden symmetry and an effective charge of 2e in the noise characteristics.

Contribution

It introduces a novel Fermi liquid framework for chargeless quasiparticles in a superconducting quantum dot system, uncovering hidden symmetries and effective charge behavior.

Findings

Back scattering noise shows an effective charge of 2e.

Strong noise suppression occurs at unitary conductance.

Mapping to the Anderson model reveals hidden U(1) symmetry.

Abstract

We construct a Fermi liquid theory to describe transport in a superconductor-quantum dot- normal metal junction close to the singlet-doublet (parity changing) transition of the dot. Though quasiparticles do not have a definite charge in this chargeless Fermi liquid, in case of particle-hole symmetry, a mapping to the Anderson model unveils a hidden U(1) symmetry and a corresponding pseudo-charge. In contrast to other correlated Fermi-liquids, the back scattering noise reveals an effective charge equal to the charge of Cooper pairs, $e^* = 2e$. In addition,we find a strong suppression of noise when the linear conductance is unitary, even for its non-linear part.

Full text

See pages - of noise_5.pdf See pages - of Supplementary_5.pdf