Control over the interactions between light and matter underlies many classical and quantum applications. In recent years, 2D layered semiconductors have gained prominence for optoelectronics because of their strong excitonic effects and capacity for van der Waals assembly. One of the unique features of these monolayer materials, the valley pseudospin, can be manipulated by controlling the local properties of optical fields. Here, we discuss two manifestations of this optical control across different regimes of coupling. In a strongly coupled regime, we discuss the dynamics of valley-polarized hybrid light-matter states, or exciton-polaritons, in a monolayer MoS2 embedded in a microcavity. Different dynamics of valley-polarized exciton-polaritons can be accessed with microcavity engineering by tuning system parameters such as cavity decay rate and exciton-photon coupling strength. Comparison of predictions and measurements demonstrate the ability to intentionally modify exciton-polariton valley characteristics, illustrating the microcavity as a tool for manipulating and engineering valley dynamics in 2D materials. In the weak coupling regime optical selection rules give rise to the valley-selective optical Stark shift. We discuss recent advances in probing this effect with improved sensitivity. Both of these complementary approaches show how the valley structure of monolayer materials yield interesting light-matter phenomena that allow tuning of optical properties.
When electronic excitations in a semiconductor interact with light, the relevant quasiparticles are hybrid lightmatter dressed states, or exciton-polaritons. In monolayer transition metal dichalcogenides, a class of 2D direct bandgap semiconductors, optical excitations selectively populate distinct momentum valleys with correlated spin projection. The combination of this spin-valley locking with photon dressed states can lead to new optical phenomena in these materials. We present spectroscopic measurements of valley-specific exciton-polaritons in monolayer 2D materials in distinct regimes. When a monolayer is embedded in a dielectric microcavity, strong coupling exciton-polaritons are achieved. Cavity-modified dynamics of the dressed states are inferred from emission. Polarization persists up to room temperature in monolayer MoS2, in contrast with bare material. We also show that distinct regimes of valley-polarized exciton-polaritons can be accessed with microcavity engineering by tuning system parameters such as cavity decay rate and exciton-photon coupling strength. Further, we report results showing that polarization-sensitive ultrafast spectroscopy can enable sensitive measurements of the valley optical Stark shift, a light-induced dressed state energy shift, in monolayer semiconductors such as WSe2 and MoS2. These findings demonstrate distinct approaches to manipulating the picosecond dynamics of valleysensitive dressed states in monolayer semiconductors.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.