From Light to Learning: Predicting Excited-State Dynamics at the Spectroscopic Frontier

Processes ranging from photosynthesis, to photocatalysis, to energy harvesting in
photovoltaic cells all begin in the same way: the absorption of light creates an exciton—a
correlated electron-hole pair that carries energy rather than charge. Exciton dynamics
and coherences determine the efficiency of energy harvesting and transport, while
excitonic manipulation enables the optical preparation and transduction of quantum
states and offers the potential to integrate the fast speed of photons into electronics.
However, quantitative predictions of exciton and other excited-state dynamics remain a
significant challenge. The first-principles understanding of exciton dynamics requires a
few basic building blocks: 1) The full exciton dispersion to capture the phase space of
momentum and energy conserving scattering processes, 2) Interaction of excitons with
external perturbations such as electromagnetic fields and lattice vibrations, and 3) An
equation of motion describing the dynamical processes. In this talk, I will discuss some of
my group’s recent developments in these directions. Firstly, we have recently measured
the exciton dispersion in a 2D materials revealing for the first time the emergence of a
massless excitons composed of massive electrons and holes [1]. Secondly, I will show
how excitons play a surprising role in nonlinear optics beyond the perturbative regime [2].
Finally, I will discuss how machine learning is opening new possibilities for simulating
excited states far beyond the reach of conventional calculations [3,4].

演講者：耶魯大學助理教授Diana Y. Qiu蒞校
時間：7/8(三) 12:00
地點：科學三館 SC353

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