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Interactions of quantum materials with strong laser fields can induce exotic non-equilibrium electronic states. Monolayer transition metal dichalcogenides, a new class of direct-gap semiconductors with prominent quantum confinement, offer exceptional opportunities for the Floquet engineering of excitons, which are quasiparticle electron–hole correlated states8. Strong-field driving has the potential to achieve enhanced control of the electronic band structure and thus the possibility of opening a new realm of exciton light–matter interactions. However, a full characterization of strong-field driven exciton dynamics has been difficult. Here we use mid-infrared laser pulses below the optical bandgap to excite monolayer tungsten disulfide and demonstrate strong-field light dressing of excitons in excess of a hundred millielectronvolts. Our high-sensitivity transient absorption spectroscopy further reveals the formation of a virtual absorption feature below the 1s-exciton resonance, which we assign to a light-dressed sideband from the dark 2p-exciton state. Quantum-mechanical simulations substantiate the experimental results and enable us to retrieve real-space movies of the exciton dynamics. This study advances our understanding of the exciton dynamics in the strong-field regime, showing the possibility of harnessing ultrafast, strong-field phenomena in device applications of two-dimensional materials.
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Ultrafast Laser Spectroscopy of Two‐Dimensional Materials Beyond Graphene
Starting with the discovery of graphene in 2004, the interest in two‐dimensional materials since then has been exponentially growing. Across many disciplines, their exceptional electrical, chemical, thermal, and optical properties have drawn considerable attention that has created an entire field within a decade of their discovery. Driven by the mechanical exfoliation technique that allows for the quick exploration of these two‐dimensional materials and their novel devices, joint efforts have been made in order to understand and exploit their potential, consequently leading to the development of their large‐scale growth. This review focuses on recent studies using ultrafast laser spectroscopy that have revealed the photocarrier dynamics in two‐dimensional materials and laid the foundation of their behavior. We provide a brief introduction on ultrafast laser spectroscopy, discuss several aspects of the photocarrier dynamics, and conclude with our perspective on future developments.
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- Award ID(s):
- 1505852
- PAR ID:
- 10026995
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 27
- Issue:
- 19
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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