Direct observation of giant binding energy modulation of exciton complexes in monolayer MoSe${}_2$

Abstract

Screening due to surrounding dielectric medium reshapes the electron-hole interaction potential and plays a pivotal role in deciding the binding energies of strongly bound exciton complexes in quantum confined monolayers of transition metal dichalcogenides (TMDs). However, owing to strong quasi-particle bandgap renormalization in such systems, a direct quantification of estimated shifts in binding energy in different dielectric media remains elusive using optical studies. In this work, by changing the dielectric environment, we show a conspicuous photoluminescence (PL) peak shift at low temperature for higher energy excitons (2s, 3s, 4s, 5s) in monolayer MoSe${}_2$, while the 1s exciton peak position remains unaltered - a direct evidence of varying compensation between screening induced exciton binding energy modulation and quasi-particle bandgap renormalization. The estimated modulation of binding energy for the 1s exciton is found to be 58.6% (70.5% for 2s, 78.9% for 3s, 85% for 4s) by coating an Al${}_2$O${}_3$ layer on top, while the corresponding reduction in quasi-particle bandgap is estimated to be 248 meV. Such a direct evidence of large tunability of the binding energy of exciton complexes as well as the bandgap in monolayer TMDs holds promise of novel device applications.

19 pages including supplemental information

References in corpus (10)

• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Tightly bound excitons in monolayer WSe2
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Magnetic brightening and control of dark excitons in monolayer WSe2
• Binding energies of exciton complexes in transition metal dichalcogenides and effect of dielectric environment
• Probing the influence of dielectric environment on excitons in monolayer WSe2: Insight from high magnetic fields
• Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer $SL-WS{e}_2$
• Exciton band structure in layered MoSe2: from a monolayer to the bulk limit
• Valley Coherent Hot Carriers and Thermal Relaxation in Monolayer Transition Metal Dichalcogenides
• Coulomb engineering of the bandgap in 2D semiconductors

Cited by in corpus (15)

• The dielectric impact of layer distances on exciton and trion binding energies in van der Waals heterostructures
• Collective Excitations in 2D Materials
• Dependence of the hBN Layer Thickness on the Band Structure and Exciton Properties of Encapsulated WSe2 Monolayers
• Layer degree of freedom for excitons in transition metal dichalcogenides
• Highly Sensitive, Fast Graphene Photodetector with Responsivity $>10^6$ A/W Using Floating Quantum Well Gate
• Asymmetrically Encapsulated vertical ITO/MoS2/Cu2O photodetector with ultra-high sensitivity
• Fundamental exciton linewidth broadening in monolayer transition metal dichalcogenides
• Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time
• Inter-layer charge transport controlled by exciton-trion coherent coupling
• Charged exctions in two-dimensional transition-metal dichalcogenides - semiclassical calculation of Berry-curvature effects
• Intricate modulation of interlayer coupling at GO/MoSe2 interface: application in time-dependent optics and device transport
• Combinatorial Large-area MoS2/Anatase-TiO2 interface: A Pathway to Emergent Optical and Opto-electronic Functionalities
• Coulomb Engineering of two-dimensional Mott materials
• Origin of selective enhancement of sharp defect emission lines in monolayer WSe${}_2$ on rough metal substrate
• Polarized and narrow excitonic emission from graphene-capped monolayer WS${}_2$ through resonant phonon relaxation