Christoph Kastl^1,2, Pietro Bonfà^3,4, Lorenzo Maserati^5,6*

1 The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

2 Walter Schottky Institute and Physik Department, Technical University of Munich, Garching 85748, Germany.

3 Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Universitá di Parma, 43124 Parma, Italy.

4 Centro S3, CNR-Istituto Nanoscienze, via Campi 213/A, I-41125 Modena, Italy

5 Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti-Pichat 6/2, 40127 Bologna, Italy

6 Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, 20133 Milan, Italy

* Corresponding authors emails: lorenzo.maserati@unibo.it

DOI10.24435/materialscloud:xf-g8 [version v2]

Publication date: Jan 09, 2023

How to cite this record

Christoph Kastl, Pietro Bonfà, Lorenzo Maserati, Anharmonic exciton-phonon coupling in metal-organic chalcogenides hybrid quantum wells, Materials Cloud Archive 2023.6 (2023), doi: 10.24435/materialscloud:xf-g8.

Description

In contrast to inorganic quantum wells, hybrid quantum wells (HQWs) based on 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 for harnessing the optoelectronic potential of HQWs. Beyond 2D metal halide perovskites, layered metal-organic chalcogenides (MOCs) are an air-stable, underexplored material class hosting room-temperature excitons that could be exploited as photodetectors, light emitting devices, and ultrafast photoswitches. Here, we elucidate the role of phonons in the optical transitions of the prototypical MOC [AgSePh]∞. Impulsive stimulated Raman scattering (ISRS) allows us to detect coherent exciton oscillations driven by Fröhlich interaction with low-energy optical phonons. Steady state absorption and Raman spectroscopies reveal a strong exciton-phonon coupling (Huang-Rhys parameter ~1.7) and its anharmonicity, manifested as non-trivial temperature-dependent Stokes shift. Our ab initio calculations support these observations, hinting at an anharmonic behavior of the low-energy phonons < 200 cm⁻¹. Our results untangle complex exciton-phonon interactions in MOCs, establishing an ideal testbed for room-temperature many-body phenomena.

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Keywords

exciton-phonon coupling metal-organic chalcogenides Raman spectroscopy