Coulomb engineering of quantum states in matter
Key phenomena in condensed matter are determined by the properties of the electronic states, strongly motivating the development of strategies for their artificial design. In semiconducting solids, heavily studied from fundamental and technological perspectives, electronic structures are currently defined using strong perturbations of the materials such as tuning the chemical composition, changing the geometry, or applying external fields. Traditional concepts, however, inherently rely on modifying single-particle properties of individual electrons, while the influence of many-particle interactions has been largely neglected in the context of bandstructure engineering so far. In addition, conventional methods start to approach intrinsic barriers in today’s technology, driving an intense search for fundamentally novel concepts.
Here, I propose to explore an alternative pathway to design and manipulate electronic states in matter that is exclusively based on many-particle interactions between electronic excitations mediated by Coulomb forces. These are exceptionally strong in two-dimensional (2D) semiconductors with a major impact on the energies of the electronic states, and are highly sensitive to the dielectric surroundings. Using layered heterostructures I intend to show how the dielectric environment of a 2D semiconductor can be tuned on ultrafast timescales by pulsed optical injection to manipulate electronic states via proximity screening. Similarly, external screening will be used to study how the geometry of proximate objects can be imprinted on the electronic structure of a 2D layer, creating dielectrically defined zero-, one-, and two-dimensional potentials in one unified system. Ultimately, the realization of rapidly tunable electronic quantum states through dielectric environment will offer novel, versatile experimental platforms for fundamental many-body physics research and establish a new approach for electronic structure engineering on the nanoscale.