Anharmonic Exciton-Phonon Coupling in Metal-Organic Chalcogenides Hybrid Quantum Wells

摘要

In contrast to inorganic quantum wells, hybrid quantum wells (HQWs) basedon metal-organic semiconductors are characterized by relatively soft lattices,in which excitonic states can strongly couple to lattice phonons. Therefore,understanding the lattice’s impact on exciton dynamics is essential forharnessing the optoelectronic potential of HQWs. Beyond 2D metal halideperovskites, layered metal-organic chalcogenides (MOCs), which are an airstable,underexplored material class hosting room-temperature excitons, canbe exploited as photodetectors, light emitting devices, and ultrafast photoswitches.Here, the role of phonons in the optical transitions of the prototypicalMOC AgSePh_∞ is elucidated. Impulsive stimulated Raman scattering(ISRS) allows the detection of coherent exciton oscillations driven by Fr?hlichinteraction with low-energy optical phonons. Steady state absorption andRaman spectroscopies reveal a strong exciton-phonon coupling (Huang-Rhysparameter ≈1.7) and its anharmonicity, manifested as a nontrivial temperaturedependentStokes shift. The ab initio calculations support these observations,hinting at an anharmonic behavior of the low-energy phonons <200 cm~(?1).These results untangle complex exciton-phonon interactions in MOCs, establishingan ideal testbed for room-temperature many-body phenomena.