Abstract: If one places a regularly ruled transparent plastic sheet on top of another identical sheet and rotates the top one while holding the bottom fixed, a beautiful moiré pattern emerges. Since 2018, researchers have created similar moiré patterns using atomically thin 2D materials like graphene or transition-metal dichalcogenides (TMDs) by precisely controlling the rotation or twist angles between layers. These moiré materials exhibit fascinating electronic and optical properties, such as superconductivity, correlated states, and trapped excitons (electrically bound pairs of holes and electrons), all tunable with the twist angle. This has generated tremendous excitement in the physics, materials science, and chemistry communities, and moiré materials are now regarded as condensed matter quantum simulators.

First principles atomistic approaches to modelling moiré materials remain a major computational challenge due to the large unit cells of the moiré superlattices. Despite significant progress in experiments, atomistic studies are few and far between. In this talk, I will describe our efforts to enable detailed atomistic calculations for phonons, low-energy electrons, and excitons. Specifically, I will discuss the emergence of new sound-wave-like modes called phasons, their impact on localized electrons, and the emergence of trapped Wannier and charge-transfer excitons.

Bio: Indrajit is a post-doctoral researcher in Prof. Ángel Rubio's group at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg. Previously, he was a Marie-Sklodowska Curie Actions Individual Fellow at Imperial College London, where he worked with Prof. Johannes Lischner and Prof. Arash Mostofi. He completed his PhD in physics at the Indian Institute of Science under the supervision of Prof. Manish Jain. He also worked as an applied physicist in the emerging technology division of Atlas Copco Group. He specializes in developing and applying ab initio methods to predict and manipulate quantum phenomena in complex materials, aiming to help experimentalists find the goldilocks materials for technological relevance.