Atomically thin two-dimensional (2D) materials represent a rapidly moving frontier of condensed matter physics. The reduced phase space and low dielectric screening equip these extremely thin materials with unique physical properties, which can be further tuned by external probes or by stacking the 2D materials into van der Waals heterostructures. In this talk, I will discuss how automated computational workflows can be used to characterize prospect 2D materials from first principles and how they can help to identify novel compounds with interesting properties such as room temperature magnetic order, non-trivial band topologies, and strong (non)linear optical response [1]. In addition to mapping out the structure and properties of >4000 pristine monolayers, we conduct a systematic study of the native point defects in about 100 of the most stable 2D semiconductors[2]. These calculations allow us to determine a range of defect-related properties such as the equilibrium Fermi level position, dupability, and the energy of charge transition levels in the band gap. Of particular interest are defects with triplet groundstate as these have potential applications in quantum technology and magnetic field sensing.  In the last part of the talk, I will discuss the fascinating physics of 2D excitons. I will describe new types of excitonic states in 2D semiconductor heterostructures [3] and illustrate how dielectric engineering provides an elegant means to modify – both quantitatively and qualitatively – the electronic excitations in a 2D materials without compromising the structural integrity of the material.

 

References:

[1] Recent progress of the Computational 2D Materials Database (C2DB), M. Gjerding et al. 2D Materials 8, 044002 (2021)

[2] Quantum point defects in 2D materials: The QPOD database, F. Bertoldo et al. arXiv:2110.01961v1

[3] Electrical tuning of optically active interlayer excitons in bilayer MoS₂, N. Peimyoo et al. Nature Nanotechnology, https://doi.org/10.1038/s41565-021-00916-1