Colloquium: “On the Nature of Exciton-Bath Interactions in Two-Dimensional Lead Halide Perovskites” — Wednesday, January 16, 2019, 4:00 PM

Dr. Ajay Ram Srimath Kandada,
Marie Sklodowska Curie Fellow (Global)
Georgia Institute of Technology,
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, January 16, 2019, at 4:00 PM

There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


Excitonic interactions in 2D semiconductors garner considerable attention, both due to their relevance in quantum opto-electronics and to the richness of their physics. Quantum-well like derivatives of organic-inorganic perovskites are emerging material systems where strongly bound two-dimensional excitons have been observed even at room temperature.1 These hybrid semiconductors feature complex lattice dynamics due to the ‘softness’ arising from non-covalent bonds between molecular moieties and the inorganic network and due to the ionic character of the crystal.2 I will discuss the profound and unique consequences of such dynamic structural complexity on the fundamental character of primary photo-excitations. I will present evidences of polaronic effects3 and multi-body correlations,2 both of which are strongly affected by the lattice dynamics, based on various ultrafast optical spectroscopies. Going beyond the conventional ultrafast optical tools, I will also discuss a new proposal to use entangled photon-pairs as probe of correlations in matter.


(1)       Neutzner, S.; Thouin, F.; Cortecchia, D.; Petrozza, A.; Silva, C.; Kandada, A. R. S. Exciton-Polaron Spectral Structures in Two Dimensional Hybrid Lead-Halide Perovskites. Phys. Rev. Mater. 2018, 2, 064605.

(2)       Thouin, F.; Neutzner, S.; Cortecchia, D.; Dragomir, V. A.; Soci, C.; Salim, T.; Lam, Y. M.; Leonelli, R.; Petrozza, A.; Kandada, A. R. S.; et al. Stable Biexcitons in Two-Dimensional Metal-Halide Perovskites with Strong Dynamic Lattice Disorder. Phys. Rev. Mater. 2018, 2, 034001.

(3)       Thouin, F.; Chávez, D. A. V.; Quarti, C.; Cortecchia, D.; Bargigia, I.; Beljonne, D.; Petrozza, A.; Silva, C.; Kandada, A. R. S. Phonon Coherences Reveal the Polaronic Character of Excitons in Two-Dimensional Lead-Halide Perovskites. Nat. Mater. 2018, in press.


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