# Dresden 2020 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 71: Correlated Electrons: Other Theoretical Topics

### TT 71.9: Vortrag

### Freitag, 20. März 2020, 11:45–12:00, HSZ 304

**Plasmons In Doped Mott Insulators** — •Andrej Lehmann, Evgeny Stepanov, and Alexander Lichtenstein — I. Institut für Theoretische Physik, Hamburg, Deutschland

Plasmons play an important role in nanophotonics and different metamaterials applications exhibiting interesting phenomena like negative refraction, superlensing and more. Plasmons are usually studied in the metallic regime, where the mobility of charge carrier density is large. Recently, correlated plasmons attracted a lot of attention in Mott-like insulating oxides showing a low loss in the visible optical range. In order to study plasmons in insulators, one has to apply doping to induce fluctuations of a charge density. Theoretically, plasmons can be described by the Lindhardt dielectric function using the random phase approximation (RPA). However, the RPA is applicable only in the weakly interacting regime, which corresponds to small-gap or metallic systems. For description of plasmons in Mott insulating regime one have to use more elaborated methods, such as the Dual Boson (DB) theory. In this work we study correlated plasmons in a single band Mott insulator with a prototype of C2F and C2H materials. For this aim we apply a ladder DB approach that considers the polarization operator in the two-particle ladder form written in terms of local three- and four-point vertex functions. Recently, it has been shown that two-particle vertex functions can be drastically simplified in the regime of strong collective fluctuations in the system. In this case the DB theory can be reduced to a much simpler RPA+EDMFT approach. Thus, we finally compare our results with results of the RPA method.