Kinetics of four-wave mixing for a 2D magneto-plasma in strong magnetic fields

TL;DR

This study explores the femtosecond kinetics of a 2D magneto-plasma under strong magnetic fields, revealing quantum beats at twice the cyclotron frequency and counterintuitive dephasing behavior influenced by Coulomb interactions.

Contribution

It provides a detailed analysis of four-wave mixing signals and dephasing dynamics in a 2D magneto-plasma, considering Landau subbands and Coulomb scattering without screening effects.

Findings

FWM signals show quantum beats at twice the cyclotron frequency.

Dephasing time decreases with increasing magnetic field due to Coulomb effects.

Dephasing behavior depends on detuning, plasma density, and pulse spectral width.

Abstract

We investigate the femtosecond kinetics of an optically excited 2D magneto-plasma at intermediate and high densities under a strong magnetic field perpendicular to the quantum well (QW). We assume an additional weak lateral confinement which lifts the degeneracy of the Landau levels partially. We calculate the femtosecond dephasing and relaxation kinetics of the laser pulse excited magneto-plasma due to bare Coulomb potential scattering, because screening is under these conditions of minor importance. In particular the time-resolved and time-integrated four-wave mixing (FWM) signals are calculated by taking into account three Landau subbands in both the valance and the conduction band assuming an electron-hole symmetry. The FWM signals exhibit quantum beats mainly with twice the cyclotron frequency. Contrary to general expectations, we find no pronounced slowing down of the dephasing with increasing magnetic field. On the contrary, one obtains a decreasing dephasing time because of the increase of the Coulomb matrix elements and the number of states in a given Landau subband. In the situation when the loss of scattering channels exceeds these increasing effects, one gets a slight increase at the dephasing time. However, details of the strongly modulated scattering kinetics depend sensitively on the detuning, the plasma density, and the spectral pulse width relative to the cyclotron frequency.