Ultrafast Nonlinear Optical Response of Strongly Correlated Systems: Dynamics in the Quantum Hall Effect Regime

TL;DR

This paper develops a theoretical framework to analyze the ultrafast nonlinear optical response of strongly correlated 2D electron systems in magnetic fields, revealing signatures of collective excitations and correlation effects in FWM spectra.

Contribution

It introduces a novel theoretical approach to separate correlated contributions in nonlinear optical responses of strongly correlated systems, highlighting non-Markovian effects and controllable correlation signatures.

Findings

Resonant enhancement of the lowest Landau level FWM signal

Strong non-Markovian dephasing of higher Landau level magnetoexcitons

Oscillatory temporal profiles of FWM signals due to quantum kinetics

Abstract

We present a theoretical formulation of the coherent ultrafast nonlinear optical response of a strongly correlated system and discuss an example where the Coulomb correlations dominate. We separate out the correlated contributions to the third-order nonlinear polarization, and identify non-Markovian dephasing effects coming from the non-instantaneous interactions and propagation in time of the collective excitations of the many-body system. We discuss the signatures, in the time and frequency dependence of the four-wave-mixing (FWM) spectrum, of the inter-Landau level magnetoplasmon (MP) excitations of the two-dimensional electron gas (2DEG) in a perpendicular magnetic field. We predict a resonant enhancement of the lowest Landau level (LL) FWM signal, a strong non-Markovian dephasing of the next LL magnetoexciton (X), a symmetric FWM temporal profile, and strong oscillations as function of time delay, of quantum kinetic origin. We show that the correlation effects can be controlled experimentally by tuning the central frequency of the optical excitation between the two lowest LLs.