Interlayer Fermi polarons of excited exciton states in quantizing magnetic fields

TL;DR

This paper investigates interlayer Fermi polarons associated with excited 2s exciton states in WSe2/graphene heterostructures under magnetic fields, revealing their evolution into distinct quasiparticle branches and enabling optical detection of quantum Hall states.

Contribution

It provides the first experimental observation of interlayer Fermi polarons for excited excitons in layered heterostructures under magnetic fields, highlighting their evolution and quantum Hall detection capabilities.

Findings

Detection of integer and fractional quantum Hall states via optical methods

Observation of 2s exciton states evolving into attractive and repulsive polarons

Insight into excited quasiparticles and Bose-Fermi mixtures in layered materials

Abstract

The study of exciton-polarons has offered profound insights into the many-body interactions between bosonic excitations and their immersed Fermi sea within layered heterostructures. However, little is known about the properties of exciton polarons with interlayer interactions. Here through magneto-optical reflectance contrast measurements, we experimentally investigate interlayer Fermi polarons for 2s excitons in WSe$_2$/graphene heterostructures, where the excited exciton states (2s) in the WSe$_2$ layer are dressed by free charge carriers of the adjacent graphene layer in the Landau quantization regime. First, such a system enables an optical detection of integer and fractional quantum Hall states (e.g. $\nu=\pm1/3$, $\pm$2/3) of monolayer graphene. Furthermore, we observe that the 2s state evolves into two distinct branches, denoted as attractive and repulsive polarons, when graphene is doped out of the incompressible quantum Hall gaps. Our work paves the way for the understanding of the excited composite quasiparticles and Bose-Fermi mixtures.