Shedding light on non-equilibrium dynamics of a spin coupled to fermionic reservoir

TL;DR

This paper investigates the non-equilibrium dynamics of a single spin in a quantum dot coupled to a fermionic reservoir, revealing a tunable, universal power-law singularity in optical absorption linked to Kondo correlations.

Contribution

It provides a detailed analysis of the non-equilibrium spin dynamics and optical absorption lineshape, connecting them to the fixed points of the Anderson Hamiltonian and Kondo physics.

Findings

Optical absorption lineshape exhibits three frequency domains corresponding to different timescales.

The power-law singularity in the lineshape is linked to Kondo correlations and is tunable.

The dynamics are described by the three fixed points of the single-impurity Anderson Hamiltonian.

Abstract

A single confined spin interacting with a solid-state environment has emerged as one of the fundamental paradigms of mesoscopic physics. In contrast to standard quantum optical systems, decoherence that stems from these interactions can in general not be treated using the Born-Markov approximation at low temperatures. Here we study the non-equilibrium dynamics of a single-spin in a semiconductor quantum dot adjacent to a fermionic reservoir and show how the dynamics can be revealed in detail in an optical absorption experiment. We show that the highly asymmetrical optical absorption lineshape of the resulting Kondo exciton consists of three distinct frequency domains, corresponding to short, intermediate and long times after the initial excitation, which are in turn described by the three fixed points of the single-impurity Anderson Hamiltonian. The zero-temperature power-law singularity dominating the lineshape is linked to dynamically generated Kondo correlations in the photo-excited state. We show that this power-law singularity is tunable with gate voltage and magnetic field, and universal.