Christian Schäfer – Chalmers University of Technoloy (Sweden)
Ab initio QED: Combining strong light-matter interaction with realistic materials and its application to chemistry
The alchemical dream of altering a given material on demand into something desirable is at the very heart of chemistry. Cavity environments provide a novel handle to non-intrusively control materials and chemistry as demonstrated by recent experimental work. A theoretical description of those systems is challenging, to put it mildly. The self-consistent interaction between complex electromagnetic environments and realistic materials gave birth to a new discipline, sometimes referred to as ’ab initio QED’, on the interface of condensed matter and quantum optics.
I will provide an introduction into this newly emerged ﬁeld, discuss important conditions , highlight its strength, current limitations and future prospects. In a ﬁrst step, a non-perturbative photon-free framework  will be introduced that provides access to strong and even deep ultra-strong-coupling phenomena by expressing quantum ﬂuctuations of the ﬁeld as ﬂuctuations of the currents. Subsequently, the left over classical Maxwell ﬁelds can be efﬁciently embedded into state-of-the-art ab initio libraries . From this perspective, the current state of ab initio QED will be brieﬂy reviewed. Finally, I will present applications to chemistry, demonstrating modiﬁcations in weak intermolecular interactions  and the speed of chemical reactions  by means of an external cavity.
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