Stroboscopic quasiparticle tracking through optical elastic scattering
Naomi S. Ginsberg, University of California, Berkeley
Interferometric scattering (iSCAT) microscopy enables ultrasensitive detection and tracking of individual particles such as proteins or nanoparticles in a wide range of contexts. We describe our recent work to instead track photoexcited species in a wide range of semiconducting and composite materials—electrons and holes, bound electron-hole pairs, heat, and sound—at the nanometer scale with similar interferometric sensitivity. Because these quasiparticles often travel nanometers over very short time scales, we follow how these different forms of energy travel through materials stroboscopically. We first introducing a confocal impulsive light pulse to generates a localized population of excited species and follow it with a widefield iSCAT probe light pulse to interferometrically detect how these species modify their index of refraction locally, generating differential contrast. I will describe a series of recent findings associated with quasiparticle transport as a function of different scales and types of material heterogeneity, elaborate on the origins of the contrast mechanism, and leverage these insights to describe the implications of imaging heat as readily as electronic energy, both separately and in combination.