Electrical control of interlayer exciton dynamics in atomically thin heterostructures

Abstract

Excitons in semiconductors, bound pairs of excited electrons and holes, can form the basis for new classes of quantum optoelectronic devices. A van der Waals heterostructure built from atomically thin semiconducting transition metal dichalcogenides (TMDs) enables the formation of excitons from electrons and holes in distinct layers, producing interlayer excitons with large binding energy and a long lifetime. Employing heterostructures of monolayer TMDs, we realize optical and electrical generation of long-lived neutral and charged interlayer excitons. We demonstrate the transport of neutral interlayer excitons across the whole sample that can be controlled by excitation power and gate electrodes. We also realize the drift motion of charged interlayer excitons using Ohmic-contacted devices. The electrical generation and control of excitons provides a new route for realizing quantum manipulation of bosonic composite particles with complete electrical tunability.As bosonic composite particles, long-lived excitons can be potentially utilized for the realization of coherent quantum many-body systems (1, 2) or as quantum information carriers (3,4). In conventional semiconductors, the exciton lifetime can be increased by constructing double quantum well (DQW) heterostructures, where spatially separated electrons and holes form interlayer excitons (IEs) across the quantum wells (5-10). Strongly bound IEs can also be formed in atomically thin DQW. By stacking two

Moiré potential impedes interlayer exciton diffusion in van der Waals heterostructures

“…This angle-dependent lifetime is confirmed in many of our hBLs prepared by the MET method. Using D IX = L IX 2 / IX , an effective diffusion coefficient is estimated to be ~50 (30) cm 2 /s for sample A-1 (A-2), larger than the typical value reported for incom-mensurate hBLs (16,20,21). The extracted value for sample C is ~0.1 cm 2 /s, consistent with previous studies (see the Supplementary Materials for details).…”

“…Moiré potential has been demonstrated to have a profound influence on the electronic and optical properties of vdW heterostructures. However, its role in exciton diffusion has been largely ignored in previous studies on hBLs consisting of TMD monolayers with rather different lattice constants or with larger twist angles (16,17,20). Our experiments present a complementary view of IX diffusion from previous studies and highlight the influence of the moiré potential on exciton diffusion in hBLs.…”

Controlling Excitons in an Atomically Thin Membrane with a Mirror

“…Manipulating the radiative processes of the emitters at a timescale faster than their lifetime can facilitate new methods to store and release photons on-demand. This may be achieved by using, for example, interlayer excitons with longer lifetimes [54,55] and material systems hosting interlayer excitons with large enough oscillator strength [56]. The lifetime of the excitons can be extended by a factor of 1/ρ, where ρ is the reflection loss of the metallic mirror, leading to significantly enhanced optical 10 nonlinearity [20].…”

Interlayer-Exciton Based Nonvolatile Valleytronic Memory

“…Van der Waals HSs stacked by TMDs monolayers enable the generation of long-lived IXs with a large binding energy of about 150 meV 1 , and a long diffusion distance over ve micrometres 2 , further extending the already appealing properties of the constituent TMDs monolayers. Since IXs are composed of electrons and holes that are resided in neighboring layers, their physical properties strongly depend on the layer con gurations and external elds or dopings [3][4][5] .…”

“…Since IXs are composed of electrons and holes that are resided in neighboring layers, their physical properties strongly depend on the layer con gurations and external elds or dopings [3][4][5] . Through electrical eld or doping, we can modulate the emission intensity and wavelength of the IX 1,6 , and even switch its polarization 7 . Recently, IX in the HSs stacked by other layered materials such as 2D perovskites and InSe with TMDs monolayer has been demonstrated and can be utilized in mid-infrared photodetections and valleytronics 8,9 .…”