Department of Physics, University of Regensburg, Germany

Since the discovery of graphene, a single sheet of carbon atoms, research focused on two-dimensional (2D) van der Waals materials evolved rapidly due the availability of atomically thin, thermally stable crystals with intriguing physical properties. The 2D materials naturally inherit major traits associated with systems of reduced dimensionality: strongly enhanced interactions, efficient light-matter coupling, and sensitivity to the environment. In particular, the considerable strength of the Coulomb forces introduces a rich variety of many-body phenomena including significant renormalization of the bandgap and the emergence of tightly bound exciton quasi-particles.

In this talk, I will show how atomically-thin crystals offer an alternative approach to nanoscale bandgap engineering, based on the local tuning of the Coulomb interaction and the environmental sensitivity of 2D materials. I will demonstrate how careful tailoring of the surrounding dielectric environment allows us to tune the electronic bandgap of single layers of semiconducting transition-metal dichalcogenides by many 100’s of meV and present an in-plane dielectric heterostructure as an illustration. The unique advantages of the Coulomb engineering in 2D, including nanometer sensitivity and a high flexibility of resulting dielectric heterostructures, will be further discussed. Finally, I will give a brief outlook towards new pathways for manipulating and designing electronic bandgaps in the 2D plane.

Alexey Chernikov received his Ph.D. from the University of Marburg (Germany) for the work on the optical properties of semiconducting materials and external cavity semiconducting lasers. With a Feodor-Lynen Fellowship from the Alexander von Humboldt Foundation, he joined the group of Tony F. Heinz at the Columbia University (New York, USA) in 2013 to study Coulomb phenomena in atomically-thin 2D systems. Currently, he leads a research group at the University of Regensburg (Germany) funded by the Emmy-Noether Initiative of the German Research Foundation. His research is focused on fundamental interactions of electronic and excitonic many-body states in nanostructured matter.