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Physics Colloquium: Carlos Silva

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January 27 | 4:00 pm - 5:00 pm

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Speaker: Carlos Silva, Georgia Tech University

Title: Exciton polarons in two-dimensional hybrid metal-halide perovskites

Abstract: While polarons — charges bound to a lattice deformation induced by electron-phonon coupling — are primary photoexcitations at room temperature in bulk metal-halide hybrid organic-inorganic perovskites (HOIP),excitons — Coulomb-bound electron-hole pairs — are the stable quasi-particles in their two-dimensional (2D) analogues. Here we address the fundamental question: are polaronic effects consequential for excitons in2D-HIOPs? Based on our recent work, we argue that polaronic effects are manifested intrinsically in the exciton spectral structure, which is comprised of multiple non-degenerate resonances with constant inter-peak energy spacing.We highlight measurements of population and dephasing dynamics that point to the apparently deterministic role of polaronic effects in excitonic properties.We contend that an interplay of long-range and short-range exciton-lattice couplings give rise to exciton polarons, a character that fundamentally establishes their effective mass and radius, and consequently, their quantum dynamics.  Given this complexity, a fundamentally far-reaching issue is how Coulomb-mediated many-body interactions—elastic scattering such as excitation-induced dephasing, inelastic exciton bimolecular scattering, and multi-exciton binding—depend upon the specific exciton-lattice coupling within the structured excitation lineshape. We measure the intrinsic and density-dependent exciton dephasing rates of the multiple excitons and their dependence on temperature by means of two-dimensional coherent excitation spectroscopy. We find that diverse excitons display distinct intrinsic dephasing rates mediated by phonon scattering involving different effective phonons, and contrasting rates of exciton-exciton elastic scattering. These findings establish specifically the consequence of distinct lattice dressing on exciton many-body quantum dynamics, which critically define fundamental optical properties that underpin photonics and quantum optoelectronics.



January 27

4:00 pm - 5:00 pm
Event Categories:
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301 Riddick Hall
2401 Stinson Dr.
Raleigh, NC United States