Laser-driven Ultrafast Dynamics of a Fractional Quantum Hall System

TL;DR

This study models the ultrafast nonequilibrium dynamics of a fractional quantum Hall system under laser excitation, revealing the excitation of magnetoplasmon and chiral-graviton modes through a two-Landau-level approximation.

Contribution

It introduces a quasi-one-dimensional model that accounts for inter-Landau level scattering, enabling the simulation of laser-driven dynamics in FQH systems beyond traditional bilayer models.

Findings

Laser pulses can excite magnetoplasmon modes in FQH systems.

Inter-Landau level scattering enables excitation of the chiral-graviton mode.

Out-of-equilibrium states exhibit rich physics with non-trivial excited modes.

Abstract

Fractional quantum Hall (FQH) systems are strongly interacting electron systems with topological order. These systems are characterized by novel ground states, fractionally charged and neutral excitations. The neutral excitations are dominated by a low-energy collective magnetoroton mode. Here we derive and use a quasi-one-dimensional model to investigate the ultrafast nonequilibrium dynamics of a laser-driven FQH system within a two-Landau-level approximation. As opposed to the traditional and synthetic bilayers, our model accounts for interactions where electrons can scatter from one Landau-level to another. By performing exact time evolution of the system, we create an out-of-equilibrium state following the laser pulse that shows rich physics. Our calculations show the presence of non-trivial excited modes. One of these modes is electromagnetically active and represent density oscillations of \emph{magnetoplasmon} mode. Another mode is identified by evaluating the overlap of the initial state and the out-of-equilibrium state following the laser pulse with a quadrupole operator. This mode is analogous to the chiral-graviton mode for FQH systems recently measured in experiments [Nature {\bf 628}, 78 (2024)]. Our results show that a linearly-polarized pulse field can excite the graviton mode when inter-Landau level scattering occurs.