Asymmetry of the excess finite-frequency noise

TL;DR

This paper investigates the asymmetry in excess finite-frequency noise in mesoscopic systems with interactions, revealing that non-linearity causes asymmetry and explaining recent experimental observations in various quantum systems.

Contribution

It demonstrates that excess noise can be asymmetric in non-linear systems and connects this phenomenon to experimental results in Josephson junctions and strongly correlated quantum systems.

Findings

Excess noise asymmetry occurs in non-linear mesoscopic systems.

The asymmetry explains recent experimental observations in Josephson junctions.

Strong asymmetry is observed in Luttinger liquid systems like quantum wires and nanotubes.

Abstract

We consider finite frequency noise in a mesoscopic system with arbitrary interactions, connected to many terminals kept at finite electrochemical potentials. We show that the excess noise, obtained by subtracting the noise at zero voltage from that at finite voltage, can be asymmetric with respect to positive/negative frequencies if the system is non-linear. This explains a recent experimental observation in Josephson junctions as well as strong asymmetry obtained in typical non-linear and strongly correlated systems described by the Luttinger liquid (LL): edge states in the fractional quantum Hall effect, quantum wires and carbon nanotubes. Another important problem where the LL model applies is that of a coherent conductor embedded in an ohmic environment.