Slow Dephasing of Coherent Optical Phonons in Two-dimensional Lead Organic Chalcogenides

TL;DR

This paper reports the discovery of long-lived coherent optical phonons in lead organic chalcogenides, a new hybrid 2D semiconductor family, with potential for advanced electronic and quantum applications due to their harmonic phonon dynamics.

Contribution

It introduces lead organic chalcogenides as a new class of hybrid semiconductors with harmonic phonon behavior and long dephasing times, contrasting with rapid dephasing in existing materials like halide perovskites.

Findings

Dephasing time up to 75 ps at 10 K.

Phonon oscillations lasting up to 500 cycles.

Harmonicity parameter exceeds that of halide perovskites by an order of magnitude.

Abstract

Hybrid organic-inorganic semiconductors with strong electron-phonon interactions provide a programmable platform for developing a variety of electronic, optoelectronic, and quantum materials by controlling these interactions. However, in current hybrid semiconductors, such as halide perovskites, anharmonic vibrations with rapid dephasing hinder the ability to coherently manipulate phonons. Here, we report the observation of long-lived coherent phonons in lead organic chalcogenides (LOCs), a new family of hybrid two-dimensional semiconductors. These materials feature harmonic phonon dynamics despite distorted lattices, combining long phonon dephasing times with tunable semiconducting properties. Dephasing time as long as 75 ps at 10 K, with up to 500 cycles of phonon oscillation between scattering events, was observed, corresponding to a dimensionless harmonicity parameter more than an order of magnitude larger than that of halide perovskites. The phonon dephasing time is significantly influenced by anharmonicity and centrosymmetry, both of which can be tuned through the design of the organic ligands thanks to the direct bonding between the organic and inorganic motifs. This research opens new opportunities for the manipulation of electronic properties with coherent phonons in hybrid semiconductors.