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Using four-wave mixing microscopy, we measure the coherent response and ultrafast dynamics of excitons and trions in MoSe$_2$ monolayers grown by molecular beam epitaxy on thin films of hexagonal boron nitride. We assess inhomogeneous and…

This letter reports a time resolved pump-probe reflectance spectroscopic study on moir\'e excitons in a twisted monolayer WS2/WSe2 heterostructure. By probing at the resonant energies of intralayer excitons, we observed their distinct…

Mesoscale and Nanoscale Physics · Physics 2024-10-08 Feng Kai , Xiong Wang , Yiqin Xie , Yuhui Yang , Kenji Watanabe , Takashi Taniguchi , Hongyi Yu , Wang Yao , Xiaodong Cui

We investigate the excitonic dynamics in MoSe2 monolayer and bulk samples by femtosecond transient absorption microscopy. Excitons are resonantly injected by a 750-nm and 100-fs laser pulse, and are detected by a probe pulse tuned in the…

Mesoscale and Nanoscale Physics · Physics 2015-06-17 Nardeep Kumar , Qiannan Cui , Frank Ceballos , Dawei He , Yongsheng Wang , Hui Zhao

The energy landscape of optical excitations in mono- and few-layer transition metal dichalcogenides (TMDs) is dominated by optically bright and dark excitons. These excitons can be fully localized within a single TMD layer, or the electron-…

Monolayer transition metal dichalcogenides, a new class of atomically thin semiconductors, possess optically coupled 2D valley excitons. The nature of exciton relaxation in these systems is currently poorly understood. Here, we investigate…

We report a photoluminescence (PL) and transient reflection spectroscopy study of exciton dynamics in monolayer transition transition-metal dichalcogenides (TMDs). PL saturation in monolayer MoSe2 occurs an excitation intensity more than…

Mesoscale and Nanoscale Physics · Physics 2015-06-22 Min Ju Shin , Dong Hak Kim , D. Lim

We have combined spatially-resolved steady-state micro-photoluminescence ($\mu$PL) with time-resolved photoluminescence (TRPL) to investigate the exciton diffusion in a WSe$_2$ monolayer encapsulated with hexagonal boron nitride (hBN). At…

Mesoscale and Nanoscale Physics · Physics 2018-05-09 F. Cadiz , C. Robert , E. Courtade , M. Manca , L. Martinelli , T. Taniguchi , K. Watanabe , T. Amand , A. C. H. Rowe , D. Paget , B. Urbaszek , X. Marie

Atomically thin semi-conductors are characterized by strongly bound excitons which govern the optical properties of the materials below and near the band edge. Efficient conversion of photons into electrical current requires, as a first…

Mesoscale and Nanoscale Physics · Physics 2016-02-15 Sten Haastrup , Simone Latini , Kirill Bolotin , Kristian Sommer Thygesen

Exciton binding energy and excited states in monolayers of tungsten diselenide (WSe2) are investigated using the combined linear absorption and two-photon photoluminescence excitation spectroscopy. The exciton binding energy is determined…

Materials Science · Physics 2015-06-19 Keliang He , Nardeep Kumar , Liang Zhao , Zefang Wang , Kin Fai Mak , Hui Zhao , Jie Shan

Tightly bound excitons in monolayer semiconductors represent a versatile platform to study two-dimensional propagation of neutral quasiparticles. Their intrinsic properties, however, can be severely obscured by spatial energy fluctuations…

We investigate the diffusion process of negatively charged excitons (trions) in WSe2 transition metal dichalcogenide monolayer. We measure time-resolved photoluminescence spatial profiles of these excitonic complexes which exhibit a…

Since the discovery of semiconducting monolayer transition metal dichalcogenides, a variety of experimental and theoretical studies have been carried out seeking to understand the intrinsic exciton population decay and valley relaxation…

Mesoscale and Nanoscale Physics · Physics 2016-05-04 Galan Moody , John Schaibley , Xiaodong Xu

Exciton dynamics dictate the evolution of photoexcited carriers in photovoltaic and optoelectronic devices. However, interpreting their experimental signatures is a challenging theoretical problem due to the presence of both electron-phonon…

Monolayers of transition-metal dichalcogenides (TMDs) are characterized by an extraordinarily strong Coulomb interaction giving rise to tightly bound excitons with binding energies of hundreds of meV. Excitons dominate the optical response…

Materials Science · Physics 2018-05-30 Samuel Brem , Gunnar Berghaeuser , Malte Selig , Ermin Malic

Charged excitons, or X$^{\pm}$-trions, in monolayer transition metal dichalcogenides have binding energies of several tens of meV. Together with the neutral exciton X$^0$ they dominate the emission spectrum at low and elevated temperatures.…

The optical properties of semiconducting transition metal dichalcogenides are dominated by both neutral excitons (electron-hole pairs) and charged excitons (trions) that are stable even at room temperature. While trions directly influence…

Mesoscale and Nanoscale Physics · Physics 2016-07-26 Kai Hao , Lixiang Xu , Philipp Nagler , Akshay Singh , Kha Tran , Chandriker Kavir Dass , Christian Schüller , Tobias Korn , Xiaoqin Li , Galan Moody

We investigate the dynamics of the exciton formation and relaxation on a picosecond time scale following a pulsed photoexcitation of a semiconductor. The study is conducted in the framework of the density matrix theory complemented with the…

Mesoscale and Nanoscale Physics · Physics 2015-12-25 Veljko Janković , Nenad Vukmirović

Optical resonators are a powerful platform to control the spontaneous emission dynamics of excitons in solid-state nanostructures. Here, we study a MoSe$_2$-WSe$_2$ van-der-Waals heterostructure that is integrated in a widely tunable open…

Charged optical excitations (trions) generated by charge carrier injection are crucial for emerging optoelectronic technologies as they can be produced and manipulated by electric fields. Trions and neutral excitons can be efficiently…

Atomic and Molecular Clusters · Physics 2021-12-23 Jiří Doležal , Sofia Canola , Pablo Merino , Martin Švec

We examine a mechanism by which excitons undergo ultrafast relaxation in common monolayer transition metal dichalcogenides. It is shown that at densities $\approx$ 1$\times$ 10$^{11}$ cm$^{-2}$ and temperatures $ \le 60$ K, excitons in well…

Mesoscale and Nanoscale Physics · Physics 2016-06-29 A. Thilagam