Trion Valley Coherence in Monolayer Semiconductors

Abstract

The emerging field of valleytronics aims to exploit the valley pseudospin of electrons residing near Bloch band extrema as an information carrier. Recent experiments demonstrating optical generation and manipulation of exciton valley coherence (the superposition of electron-hole pairs at opposite valleys) in monolayer transition metal dichalcogenides (TMDs) provide a critical step towards control of this quantum degree of freedom. The charged exciton (trion) in TMDs is an intriguing alternative to the neutral exciton for control of valley pseudospin because of its long spontaneous recombination lifetime, its robust valley polarization, and its coupling to residual electronic spin. Trion valley coherence has however been unexplored due to experimental challenges in accessing it spectroscopically. In this work, we employ ultrafast two-dimensional coherent spectroscopy to resonantly generate and detect trion valley coherence in monolayer MoSe${}_2$ demonstrating that it persists for a few-hundred femtoseconds. We conclude that the underlying mechanisms limiting trion valley coherence are fundamentally different from those applicable to exciton valley coherence. Based on these observations, we suggest possible strategies for extending valley coherence times in two-dimensional materials.

References in corpus (14)

• The Valley Hall Effect in MoS2 Transistors
• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Fermi polaron-polaritons in charge-tunable atomically thin semiconductors
• Exciton Radiative Lifetime in Transition Metal Dichalcogenide Monolayers
• Exciton band structure of monolayer MoS2
• Trion induced negative photoconductivity in monolayer MoS2
• Many-Body Theory of Trion Absorption Features in Two-Dimensional Semiconductors
• Ultrafast Manipulation of Valley Pseudospin
• Neutral and Charged Inter-Valley Biexcitons in Monolayer MoSe${}_2$
• Exciton Dynamics in Monolayer Transition Metal Dichalcogenides
• Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers
• Polarization and time-resolved photoluminescence spectroscopy of excitons in MoSe2 monolayers
• Long-Lived Valley Polarization of Intra-Valley Trions in Monolayer WSe2
• Coherent and Incoherent Coupling Dynamics between Neutral and Charged Excitons in Monolayer MoSe2

Cited by in corpus (15)

• Moiré Excitons Correlated with Superlattice Structure in Twisted WSe${}_2$/WSe${}_2$ Homobilayers
• Many-Body Simulation of Two-Dimensional Electronic Spectroscopy of Excitons and Trions in Monolayer Transition-Metal Dichalcogenides
• Exciton-polaron interactions in monolayer WS${}_2$
• Strain control of exciton and trion spin-valley dynamics in monolayer transition metal dichalcogenides
• Valley Degree of Freedom in Two-Dimensional van der Waals Materials
• Inter-layer charge transport controlled by exciton-trion coherent coupling
• Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time
• Disorder Dependent Valley Properties in Monolayer WSe2
• Spin-valley dynamics in alloy-based transition metal dichalcogenide heterobilayers
• Inducing room-temperature valley polarization of excitonic emission in transition metal dichalcogenide monolayers
• Gate-tunable trion switch for excitonic device applications
• Large trion binding energy in monolayer WS${}_2$ via strain-enhanced electron-phonon coupling
• Fundamentals of heterodyne wave mixing spectroscopy: a tutorial
• Assessment of valley coherence in a high-quality monolayer molybdenum diselenide
• Momentum-resolved two-dimensional spectroscopy as a probe of nonlinear quantum field dynamics