Experimental observation of Anderson localization in laser-kicked molecular rotors

TL;DR

This study experimentally demonstrates Anderson localization in quantum molecular rotors by using a laser pulse train to excite nitrogen molecules, observing exponential angular momentum distribution and the effects of noise on localization.

Contribution

First direct experimental observation of Anderson localization in true quantum kicked rotors using molecular systems with detailed analysis of noise effects.

Findings

Exponential angular momentum distribution confirms Anderson localization.

Localization length depends on kick strength.

Timing and amplitude noise destroy localization and restore diffusion.

Abstract

We observe and study the phenomenon of Anderson localization in a system of true quantum kicked rotors. Nitrogen molecules in a supersonic molecular jet are cooled down to 27~K and are rotationally excited by a periodic train of 24~high-intensity femtosecond pulses. Exponential distribution of the molecular angular momentum - the most unambiguous signature of Anderson localization - is measured directly by means of coherent Raman scattering. We demonstrate the suppressed growth of the molecular rotational energy with the number of laser kicks and study the dependence of the localization length on the kick strength. Both timing and amplitude noise in the pulse train is shown to destroy the localization and revive the diffusive growth of angular momentum.