Interactions between out-of-plane dipoles in bosonic gases enable the long-range propagation of excitons. The lack direct control over collective dipolar properties has so far limited degrees tunability and microscopic understanding exciton transport. In this work we modulate layer hybridization interplay many-body interactions excitons a van der Waals heterostructure with an applied vertical electric field. By performing spatiotemporally resolved measurements supported by theory, uncover...

Monolayer semiconductors with suppressed environmental disorder from encapsulation in high-quality insulators provide a versatile platform to study the propagation of excitonic quasiparticles at ambient conditions. Using time-resolved emission microscopy, authors monitored linear and nonlinear exciton diffusion single layers tungsten disulfide, observing highly mobile excitons nonmonotonic density dependence diffusion. Combining experiment theory, discuss impact multivalley band structure,...

The interplay of optics, dynamics and transport is crucial for the design novel optoelectronic devices, such as photodetectors solar cells. In this context, transition metal dichalcogenides (TMDs) have received much attention. Here, strongly bound excitons dominate optical excitation, carrier diffusion processes. While first two been intensively studied, there a lack fundamental understanding non-equilibrium phenomena associated with exciton that central importance e.g. high efficiency light...

The dynamics of momentum-dark exciton formation in transition metal dichalcogenides is difficult to measure experimentally, as many momentum-indirect states are not accessible optical interband spectroscopy. Here, we combine a tunable pump, high-harmonic probe laser source with 3D momentum imaging technique map photoemitted electrons from monolayer WS2. This provides momentum-, energy- and time-resolved access excited on an ultrafast time scale. high temporal resolution the setup allows us...

Abstract Transport of charge carriers is at the heart current nanoelectronics. In conventional materials, electronic transport can be controlled by applying electric fields. Atomically thin semiconductors, however, are governed excitons, which neutral electron-hole pairs and as such cannot electrical Recently, strain engineering has been introduced to manipulate exciton propagation. Strain-induced energy gradients give rise funneling up a micrometer range. Here, we combine spatiotemporal...

Atomically thin semiconductors such as transition metal dichalcogenide (TMD) monolayers exhibit a very strong Coulomb interaction, giving rise to rich exciton landscape. This makes these materials highly attractive for efficient and tunable optoelectronic devices. In this article, we review the recent progress in understanding of optics, dynamics transport, which crucially govern operation TMD-based We highlight impact hBN-encapsulation, reveals plethora many-particle states optical spectra,...

The density-driven transition of an exciton gas into electron–hole plasma remains a compelling question in condensed matter physics. In two-dimensional metal dichalcogenides, strongly bound excitons can undergo this phase change after transient injection pairs. Unfortunately, unavoidable nanoscale inhomogeneity these materials has impeded quantitative investigation elusive transition. Here, we demonstrate how ultrafast polarization nanoscopy capture the Mott through density-dependent...

Dark excitons, living for over hundreds of picoseconds as opposed to short-lived bright ones, enable the study exciton diffusion in 2D transition-metal dichalcogenides under thermal equilibrium conditions.

The optical response of doped monolayer semiconductors is governed by trions, i.e. photoexcited electron-hole pairs bound to doping charges. While their photoluminescence (PL) signatures have been identified in experiments, a microscopic model consistently capturing bright and dark trion peaks still lacking. In this work, we derive generalized PL formula on quantum-mechanical footing, considering direct phonon-assisted recombination mechanisms. We show the energy landscape...

Atomically thin semiconductors have been in the center of one most active research fields. Here, we discuss main challenges exciton transport that is crucial for nanoelectronics. We focus on phenomena monolayers, lateral heterostructures, and twisted heterostacks transition metal dichalcogenides. In this Comment, authors current status, challenges, potential technological impact dichalcogenide (TMD) vertical heterostructures as well moiré excitons TMD heterostacks.

Van der Waals heterostructures constitute a platform for investigating intriguing many-body quantum phenomena. In particular, transition-metal dichalcogenide (TMD) heterobilayers host long-lived interlayer excitons which exhibit permanent out-of-plane dipole moments. Here, we develop microscopic theory exciton-exciton interactions including both the dipolar nature of as well their fermionic substructure, gives rise to an attractive exchange. We find that these contribute drift force...

Transition metal dichalcogenide heterostructures provide a versatile platform to explore electronic and excitonic phases. As the excitation density exceeds critical Mott density, interlayer excitons are ionized into an electron-hole plasma phase. The transport of highly non-equilibrium is relevant for high-power optoelectronic devices but has not been carefully investigated previously. Here, we employ spatially resolved pump-probe microscopy investigate spatial-temporal dynamics hot-plasma...

Abstract Moiré materials provide a remarkably tunable platform for topological and strongly correlated quantum phases of matter. Very recently, the first Abelian fractional Chern insulators (FCIs) at zero magnetic field have been experimentally demonstrated, it has theoretically predicted that non-Abelian states with Majorana fermion excitations may be realized in nearly dispersionless minibands these systems. Here, we telltale evidence based on many-body exact diagonalization even more...

Abstract Monolayers of transition metal dichalcogenides have a remarkable excitonic landscape with deeply bound bright and dark exciton states. Their properties are strongly affected by lattice distortions that can be created in controlled way via strain. Here, we perform joint theory-experiment study investigating diffusion strained tungsten disulfide (WS 2 ) monolayers. We reveal non-trivial non-monotonic influence Lattice deformations give rise to different energy shifts for excitons...

Perovskites have attracted much attention due to their remarkable optical properties. While it is well established that excitons dominate response, the impact of higher excitonic states and formation phonon sidebands in spectra still need be better understood. Here, we perform a theoretical study on properties monolayered hybrid organic perovskites -- supported by temperature-dependent photoluminescence measurements. Solving Wannier equation, obtain microscopic access Rydberg-like series...

The exceptionally strong Coulomb interaction in semiconducting transition-metal dichalcogenides (TMDs) gives rise to a rich exciton landscape consisting of bright and dark states. At elevated densities, excitons can interact through exciton-exciton annihilation (EEA), an Auger-like recombination process limiting the efficiency optoelectronic applications. Although EEA is well-known particularly important atomically thin semiconductors determining lifetimes affecting transport at its...

Electrical field tuning of hybrid exciton–exciton interactions in WSe 2 homobilayers.

While exciton relaxation in monolayers of transition metal dichalcogenides (TMDs) has been intensively studied, spatial diffusion received only a little attention - spite being key process for optoelectronics and having already shown interesting unconventional behaviours (e.g. halos). Here, we study the spatiotemporal dynamics TMD track optically excited excitons time, momentum, space. In particular, investigate temperature-dependent including remarkable landscape constituted by bright dark...

Pulsed laser excitation at high pump fluences inducing an exciton Mott transition to electron–hole plasma in the as-exfoliated TMD samples room temperature.

Abstract Layered halide perovskites exhibit remarkable optoelectronic properties and technological promise, driven by strongly bound excitons. The interplay of spin‐orbit exchange coupling creates a rich excitonic landscape, determining their optical signatures exciton dynamics. Despite the dark ground state, surprisingly efficient emission from higher‐energy bright states has puzzled scientific community, sparking debates on relaxation mechanisms. Combining low‐temperature magneto‐optical...

Abstract Ultrafast charge separation after photoexcitation is a common phenomenon in various van-der-Waals (vdW) heterostructures with great relevance for future applications light harvesting and detection. Theoretical understanding of this converges towards coherent mechanism through transfer states accompanied by energy dissipation into strongly coupled phonons. The detailed microscopic pathways are material specific as they sensitively depend on the band structures individual layers,...

Optical and transport properties of doped monolayer semiconductors are dominated by trions, which three-particle compounds formed two electrons one hole or vice versa. In this work, we investigate the trion-phonon interaction on a microscopic footing apply our model to exemplary case molybdenum diselenide (${\mathrm{MoSe}}_{2}$) monolayer. We determine trion series states their internal quantum structure solving Schr\"odinger equation. Transforming system into basis equations motion,...

Low-temperature photoluminescence (PL) of hBN-encapsulated monolayer tungsten diselenide (WSe$_2$) shows a multitude sharp emission peaks below the bright exciton. Some them have been recently identified as phonon sidebands momentum-dark states. However, exciton dynamics behind emergence these has not revealed yet. In this joint theory-experiment study, we theoretically predict and experimentally observe time-resolved PL providing microscopic insights into thermalization hot excitons formed...