2D polaritons for optoelectronic devices and networks

The rate of information growth corresponds to an annual increase of 19%, reaching 100 zettabytes by the end of 2022, and novel optoelectronic tools are required for fast information processing. With perpetual generation and flow of information around, increasing the bit rates of devices that process information is imperative for sustainable future. Typically, optical signals - photons - are sent over fibre links, and that is how majority of internet traffic flows. However, photons do not interact with each other, unless they couple to a medium in which they propagate. One way to act is converting light into electronic signals, and processing signals with conventional electronics. However, in this case Ohmic losses reduce energy efficiency and processing speed is defined by electronic timescales. A distinct way to process light relies on strong light-matter coupling. When photons are coupled strongly to optical transitions and particles in semiconductors, they become hybrid light-matter particles - polaritons. Polaritons acquire nonlinearity and allow for information processing in an all-optical way. The efficiency of this process largely depends on many-body properties on materials used for building optical devices.

The project aims to develop a distinct family of optoelectronic devices by exploiting many-body interactions in semiconducting bilayers. Recent results show a highly nonlinear polaritonic response in systems of transition metal dichalcogenides (TMDCs) when these 2D materials are doped with excessive charge (for instance, free electrons). In bilayer geometry, they reveal a zoo of various intralayer and interlayer quasiparticles based on bound electron-hole pairs correlated with electrons. By coupling these quasiparticles to light, we expect that strong coupling merged with many-body interactions will lead to game-changing increase of polaritonic nonlinearity. However, accessing this physics requires developing new theoretical tools that can capture strong correlations in such a system. Many other properties needed for building polaritonic circuits and processing units are yet to be explored.

In the project, we aim to develop a theoretical description of 2D polaritons in transition metal dichalcogenides and propose blueprints for optoelectronic devices that use polaritonic many-body interactions. Our project is structured around three objectives.
1. We will develop a theoretical description of nonlinear response in doped TMDC bilayers in order to characterise many-body interactions of 2D polaritons.
2. We will study nontrivial transport properties of doped TMDC bilayers to design polaritonic circuits based on many-body interactions.
3. We will use highly nonlinear polaritonic lattices in TMDC heterobilayers to develop polaritonic computational networks.
As a result, we will develop the background for future 2D polaritonic devices based on highly nonlinear bilayer systems.