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<p class="MsoNormal"><span style="font-size:15.0pt">There will be a <b><span style="color:red">virtual</span></b><span style="color:red">
</span>Modern Optics and Spectroscopy Seminar held next<b> Tuesday, May 3 at 12pm.
</b>A short Q&A segment will immediately follow the conclusion of the seminar.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:15.0pt">Zoom link:<i><span style="color:red">
<a href="https://mit.zoom.us/j/98076834433?pwd=eTRIR2xOdDdHTFF0SmErcHFEclVyZz09">
<span style="color:red">https://mit.zoom.us/j/98076834433?pwd=eTRIR2xOdDdHTFF0SmErcHFEclVyZz09</span></a></span><br>
</i>Password: <span style="color:red">836631</span><o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span style="font-size:15.0pt">__________________________</span></b><o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:18.0pt"><br>
Aaron M. Lindenberg<br>
</span></b><b><span style="font-size:17.0pt">Stanford University</span></b><i><span style="font-size:14.0pt"><br>
<br>
</span></i><b><i><span style="font-size:16.0pt">“Exciton-driven dynamic symmetry changes and concerted lattice distortions in perovskite quantum dots”<br>
<br>
</span></i></b><i><span style="font-size:13.0pt">A central problem in condensed matter physics is to understand the fundamental coupling mechanisms between electrons and ions and the emergent phenomena that arise from these microscopic interactions. In this
talk I will describe recent femtosecond-resolved electron scattering experiments probing the dynamic microscopic interactions between excitons and the lattice in a class of lead-halide hybrid perovskite quantum dots. Understanding the origins of electron-phonon
coupling in these materials is key to interpreting and leveraging their unique optoelectronic properties. I will show how our measurements enable direct visualization and quantification of exciton-lattice coupling, leading to an ultrafast increase in symmetry
through reduction in octahedral tilts. We further demonstrate that the symmetry enhancing reorganizations induced by each exciton in a multi-excitonic state constructively interfere, giving rise to a coupling strength which scales quadratically with exciton
number. This super-linear scaling induces phonon-mediated attractive interactions between excitons in lead halide perovskites and opens up new opportunities for controlling dynamic disorder in polymorphic structures. <o:p></o:p></span></i></p>
<p class="MsoNormal"><i><br>
_____________________</i><i><span style="font-size:11.0pt"><br>
</span></i> <o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt">Christine Brooks</span></b><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Administrative Assistant</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Massachusetts Institute of Technology</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Department of Chemistry</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">77 Massachusetts Ave, 6-333</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Cambridge, MA 02139</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">p: 617.253.7239</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">e: <a href="mailto:cbrooks@mit.edu">cbrooks@mit.edu</a></span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
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