Colloquium- “Nanoscale emitters: from universal intermittency to superfluorescence” with Prof. Boldizsar Janko
November 1, 2023
3:00 PM - 4:45 PM
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Speaker: Prof. Boldizsar Janko, Notre Dame
Title: Nanoscale emitters: from universal intermittency to superfluorescence
The 2023 Chemistry Nobel Prize was awarded to Moungi Bawendi, Louis Brus and Aleksey Yekimov for the discovery and synthesis of quantum dots. In this colloquium I will discuss the remarkable optical response of these nanoscale emitters. Virtually all known fluorophores exhibit mysterious episodes of emission intermittency. A remarkable feature of the phenomenon is a power-law distribution of on- and off-times observed in colloidal semiconductor quantum dots, nanorods, nanowires and some organic dyes. More recently, fluorescence intermittency has also been detected in a quasi-two dimensional material: reduced graphene oxide.
For nanoparticles, the resulting power law extends over an extraordinarily wide dynamic range: nine orders of magnitude in probability density and five to six orders of magnitude in time. Exponents hover about the ubiquitous value of -3/2. Dark states routinely last for tens of seconds—practically forever on quantum mechanical timescales. Despite such infinite states of darkness, the dots miraculously recover and start emitting again. Although the underlying microscopic mechanism responsible for this phenomenon remains a mystery and many questions persist, I argue that substantial theoretical progress has been made. Within a single phenomenological framework we succeeded to capture the universal behavior of a wide range of nanoscale emitters and, in some cases, to reveal microscopic scenarios that could lead to emission intermittency and optical 1/f noise in these systems.
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