Novel Quantum States of Exciton–Floquet Composites: Electron–Hole Entanglement and Information

Abstract

Coulomb exchange between distinct electron−hole modes, i.e., exciton and Floquet states, in two-dimensional semiconductors is explored. Coherent ultrafast mixing of the exciton and Floquet states under weak optical pumping is investigated through a theoretical description of time-resolved and angle-resolved photoemission spectroscopy (tr-ARPES) in an extended Haldane model that includes the electron−hole Coulomb interaction. Two branches of novel quantum states are found in the form of bosonic exciton−Floquet composites, which result from exchange coupling due to the Coulomb interaction. Furthermore, tr-ARPES could be directly employed for the density matrix element of the biparticle subsystem of photoelectron and hole, and electron−hole entanglement and information could be further explored. This finding suggests a unique platform to study the buildup and dephasing of novel exciton−Floquet composites and to resolve the information carried by them, which would enable the pursuit of new reconfigurable devices based on twodimensional semiconductors.