Quantum Criticality out of Equilibrium: Steady State in a Magnetic Single-Electron Transistor

TL;DR

This paper investigates the non-equilibrium steady state of a magnetic single-electron transistor near quantum criticality, revealing universal scaling behaviors in current-voltage characteristics and decoherence properties.

Contribution

It provides an exact quantum Boltzmann approach in a large-N limit to analyze non-equilibrium quantum critical systems, specifically focusing on the Kondo effect destruction.

Findings

Universal scaling functions for I-V characteristics derived

Scaling properties of fluctuation-dissipation ratios analyzed

Decoherence properties of the local spin response elucidated

Abstract

Quantum critical systems out of equilibrium are of extensive interest, but are difficult to study theoretically. We consider here the steady state limit of a single electron transistor, which is attached to ferromagnetic leads and subjected to a finite bias voltage (V). In equilibrium (i.e., V=0), this system undergoes a continuous quantum phase transition with a critical destruction of the Kondo effect. We construct an exact quantum Boltzmann treatment in a dynamical large-N limit, and determine the universal scaling functions for the I-V characteristics covering both the linear and non-linear regimes. We also elucidate the scaling properties of both the fluctuation-dissipation ratios and the decoherence properties as encoded in the local spin response.