"Dressed Excitons" in a Multiple-Quantum-Well Structure: Evidence for an Optical Stark Effect with Femtosecond Response Time

Observation of Intervalley Biexcitonic Optical Stark Effect in Monolayer WS2

“…Prior research has demonstrated that monolayer TMDs driven by below-resonance (red-detuned) circularly polarized light can exhibit an upshifted exciton level, either at the K or K valleys depending on the helicity, while keeping the opposite valley unchanged. This valley-specific phenomenon arises from the exciton state repulsion by the photon-dressed state in the same valley, a mechanism consistent with other optical Stark effects in solids [7,8].…”

“…Prior research has demonstrated that monolayer TMDs driven by below-resonance (red-detuned) circularly polarized light can exhibit an upshifted exciton level, either at the K or K valleys depending on the helicity, while keeping the opposite valley unchanged. This valley-specific phenomenon arises from the exciton state repulsion by the photon-dressed state in the same valley, a mechanism consistent with other optical Stark effects in solids [7,8].Despite much recent progress, a complete understanding of the optical Stark effect in monolayer TMDs is still lacking. First, the anticipated complementary effect of using above-resonance (blue-detuned) light to downshift the exciton level has not been demonstrated.…”

“…Such a model has been successfully applied to describe the light-dressed states in many semiconductor systems, and can readily be adopted to describe the exciton-biexciton system [5,7,8,[31][32][33]. By virtue of the unique valley selection rules in this system, the originally 4×4 Hamiltonian matrix can be simplified into two decoupled 2×2 Hamiltonian matriceŝ…”

Witnessing the formation and relaxation of dressed quasi-particles in a strongly correlated electron system

“…2c are normalized to the energy absorbed by the sample for E pump ¼ 3.1 eV (solid blue curve) and E pump ¼ 0.95 eV (solid red curve), respectively (see Methods for details). Although in a different physical context, it is worth mentioning here that ultrafast responses to an optical pump below the gap in multiple quantum wells 28 and below the electronic excitation energy in molecular systems 29 has been previously reported.…”

Manifestation of the optical Stark effect in differential transmission spectra

“…In particular, there has been considerable interest in the investigation of the optical Stark effect (OSE), i. e. light-induced shift of energy levels in the presence of non-resonant laser fields in nanoscale materials [4]. Optical spectroscopy methods count among the most versatile and routine ones for characterizing strong-field limit of light-matter interaction in such kind of quantum systems.…”