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Monolayer transition-metal dichalcogenides, such as WSe$_2$, are direct gap, multi-valley semiconductors. Long-range electron-hole exchange interactions mix the valleys, yielding dispersion relations for massive ($\propto Q^2$) as well as…
Increasing the speed limits of conventional electronics requires innovative approaches to manipulate other quantum properties of electrons besides their charge. An alternative approach utilizes the valley degree of freedom in…
The polarization analysis of optical transitions in monolayer and bilayer transition-metal dichalcogenides provides invaluable information on the spin and valley (pseudospin) degrees of freedom. To explain optical properties of a given…
The valley degree of freedom in atomically thin transition-metal dichalcogenides provides a natural binary index for information processing. Exciton-polaritons formed under strong light-matter coupling offer a promising route to overcome…
Coherence is a crucial requirement to realize quantum manipulation through light-matter interactions. Here we report the observation of anomalously robust valley polarization and valley coherence in bilayer WS2. The polarization of the…
Nonlinear optical frequency conversion, in which optical fields interact with a nonlinear medium to produce new field frequencies, is ubiquitous in modern photonic systems. However, the nonlinear electric susceptibilities that give rise to…
We show room temperature valley coherence with in MoS2, MoSe2, WS2 and WSe2 monolayers using linear polarization resolved hot photoluminescence (PL), at energies close to the excitation - demonstrating preservation of valley coherence…
Underpinning the field of "valleytronics" is the coupling of the helicity of circularly polarized light to the valley degree of freedom, and this remains the only known lightform to exhibit this remarkable effect. Here we show that on…
Strong coupling between light and matter in an optical cavity provides a pathway to giant polariton nonlinearity, where effective polariton-polariton interactions are mediated by materials' nonlinear responses. The pursuit of such enhanced…
Abstract The valley degree of freedom in two-dimensional materials provides an opportunity to extend the functionalities of valleytronics devices. Very short valley lifetimes demand the ultrafast control of valley pseudospin. Here, we…
Single-layer semiconducting transition-metal dichalcogenides, lacking point inversion symmetry, provide an efficient platform for valleytronics, where the electronic, magnetic, valley and lattice degrees of freedom can be selectively…
Excitons are key to the optoelectronic applications of van der Waals semiconductors with the potential for versatile on-demand tuning of properties. Yet, their electrical manipulation is complicated by their inherent charge neutrality and…
While conventional semiconductor technology relies on the manipulation of electrical charge for the implementation of computational logic, additional degrees of freedom such as spin and valley offer alternative avenues for the encoding of…
We have investigated the exciton fine structure in atomically thin WSe2 -based van der Waals heterostructures where the density of optical modes at the location of the semiconductor monolayer can be tuned. The energy splitting $\Delta$…
Coherent optical dressing of quantum materials offers technological advantages to control their electronic properties, such as the electronic valley degree of freedom in monolayer transition metal dichalcogenides (TMDs). Here, we observe a…
The interactions between charges and excitons involve complex many-body interactions at high densities. The exciton-polaron model has been adopted to understand the Fermi sea screening of charged excitons in monolayer transition metal…
WSe$_2$ monolayers with variable doping are an ideal system to study two-dimensional excitonic complexes. Here, we find that the strongest photoluminescence from bright neutral excitons occurs at moderate $p$-doping levels, owing to a rapid…
The coupled spin-valley physics in transition metal dichalcogenides (TMDs) endows exciton states with valley degrees of freedom, making them promising for valleytronic applications in TMDs monolayers and/or their heterostructures. Although…
Heterostructures comprising different monolayer semiconductors provide a new system for fundamental science and device technologies, such as in the emerging field of valleytronics. Here, we realize valley-specific interlayer excitons in…
We present a proposal for achieving light-induced superconductivity using exciton polaritons - hybrid light-matter particles of excitons (bound electron-hole pairs) and microcavity photons. In contrast to previous theories of…