Valley Phonons and Exciton Complexes in a Monolayer Semiconductor

Abstract

The coupling between spin, charge, and lattice degrees of freedom plays an important role in a wide range of fundamental phenomena. Monolayer semiconducting transitional metal dichalcogenides have emerged as an outstanding platform for studying these coupling effects because they possess unique spin-valley locking physics for hosting rich excitonic species and the reduced screening for strong Coulomb interactions. Here, we report the observation of multiple valley phonons, phonons with momentum vectors pointing to the corners of the hexagonal Brillouin zone, and the resulting exciton complexes in the monolayer semiconductor WSe2. From Lande g-factor and polarization analyses of photoluminescence peaks, we find that these valley phonons lead to efficient intervalley scattering of quasi particles in both exciton formation and relaxation. This leads to a series of photoluminescence peaks as valley phonon replicas of dark trions. Using identified valley phonons, we also uncovered an intervalley exciton near charge neutrality, and extract its short-range electron-hole exchange interaction to be about 10 meV. Our work not only identifies a number of previously unknown 2D excitonic species, but also shows that monolayer WSe2 is a prime candidate for studying interactions between spin, pseudospin, and zone-edge phonons.

to appear in Nature Communications

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Cited by in corpus (13)

• Multipath optical recombination of intervalley dark excitons and trions in monolayer WSe${}_2$
• Nonclassical Exciton Diffusion in Monolayer WSe2
• Excitonic complexes in $n$-doped WS${}_2$ monolayer
• Intrinsic Donor-Bound Excitons in Ultraclean Monolayer Semiconductors
• Chiral phonons in honeycomb sublattice of layered CoSn-like compounds
• Visualization of dark excitons in semiconductor monolayers for high-sensitivity strain sensing
• Up- and Down-Conversion between Intra- and Inter-Valley Excitons in Waveguide Coupled Monolayer WSe2
• Interlayer exciton-polaron in atomically thin semiconductors
• Excited-State Trions in Two Dimensional Materials
• The effect of dielectric environment on the brightening of neutral and charged dark excitons in WSe${}_2$ monolayer
• Flexural deformations and collapse of bilayer two-dimensional crystals by interlayer exciton
• Hybrid dark excitons in monolayer ${MoS}_2$
• Laser-patterned submicron Bi2Se3-WS2 pixels with tunable circular polarization at room temperature