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Controlling light-matter interactions by quantum designed 2D materials

Periodic Reporting for period 2 - LIMA (Controlling light-matter interactions by quantum designed 2D materials)

Reporting period: 2019-10-01 to 2021-03-31

The overarching idea of LIMA is to use advanced quantum mechanical computer simulations to perform rational design of new materials with tailored optical properties that can be used for high-efficiency solar cells and single- photon quantum technologies, respectively. In terms of materials, the focus is primarily, but not exclusively, on atomically thin two-dimensional (2D) materials, which represent an emergent class of materials with quite distinct properties as compared to conventional bulky materials. One important specific aim is the identification of novel layered structures composed of 2D materials stacked in a carefully designed sequence with potential to reach solar-to-electricity power conversion efficiencies in excess of 50%. Another specific goal is to find stable point defects in wide band gap insulators that can be used to realize “on demand” single photon light sources - a fundamental prerequisite for several emergent quantum technologies including quantum communication. To reach these goals, the project will develop computational methods for quantifying the non-radiative losses that limit light-matter interactions, and thereby enable a realistic assessment of the actual performance of a given material. With its rational approach to materials design, LIMA will help to accelerate the development of new and improved optical materials to the benefit of our economy and society.
An important milestone was the launching of the Computational 2D Materials Database (C2DB) – a fully open and searchable online database containing structures and a variety of electronic, optical and magnetic properties for more than 4000 2D materials (https://cmr.fysik.dtu.dk/c2db/c2db.html). The C2DB has subsequently formed the basis for high-throughput screening studies where a number of novel 2D ferromagnetic semiconductors and topological insulators have been identified. A new type of 2D materials with broken mirror symmetries – the so-called Janus monolayers – have been investigated, and their potential as building blocks for advanced opto-electronic devices has been demonstrated and disseminated in several papers. In collaboration with Frank Koppens at ICFO, Barcelona, we have studied intersubband transitions in van der Waals quantum wells consisting of a few-layer stacks of 2D semiconductors, as a novel platform for light-matter interactions.
The C2DB computational database launched by LIMA in 2018 is by far the largest and most comprehensive (in terms of calculated and stored properties) of its kind and represent a significant step beyond the state of the art. The work on intersubband transitions in ultrathin van der Waals materials (published in Nature Nanotechnology) represents a completely new concept with an interesting potential for optical devices in the mid-infrared frequency regime. For the remaining 3.5 years of the project period, I will expand the C2DB further by including multilayer structures, point defects, etc. and establish it as the main reference source for 2D materials research. I will develop a computational platform that allows for a complete and realistic assessment of the key optical parameters of semiconductors including defect types and concentration, non-radiative lifetimes, photoluminescence spectra and photovoltaic power conversion efficiencies. This platform will be used to identify specific designs of multilayer solar cells based on 2D material heterostructures as well as particular point defect systems for efficient generation of single photons with ideal characteristics beyond the current state of the art (NV centers in diamond).
LIMA at a glance