ERC starting grant on Top-Down Superlattice Engineering of 2D Quantum Matter

One of the pillars of today’s nanotechnology is the ability to precisely control the spatial symmetries and spatial extents of quantum states confined into nanostructures, either by top-down or bottom-up approaches. An intriguing case are superlattice structures, where a nanoscale periodic potential is superimposed onto the periodic atomic arrangement of a solid-state material. These superlattices give rise to artificial condensed matter phases with emergent quantum electronic properties fully controlled by the shape, magnitude and symmetry of the external potential.

Our recent ERC starting grant project "Top-Down Superlattice Engineering of 2D Solid-State Quantum Matter" investigates emergent quantum states in such nanofabricated superlattice structures. The project focuses on two-dimensional materials with strong spin-orbit coupling and non-trivial band topologies to establish their potential as functional spin-electronic and optoelectronic devices in semiconductor and quantum technologies.

2DTopS is funded through the European Union’s Horizon Europe Research and Innovation Programme under Grant Agreement No 101076915. 

Control of symmetry and topology in van der Waals heterostructures

Van der Waals materials and their heterostructure are an ideal platform to engineer and explore topological states. We can control and break the relevant symmetries of the Hamiltonian at will by interfacing different van der Waals materials with different symmetries. 

Currently, we explore spin-orbit and magnetic proximity interactions in graphene-based vdW heterostructures of 2D materials on a fundamental level. We study the spintronic and magnetotransport properties of the heterostructures and their control via charge tuning, layer number, quality of the material interfaces, as well as the crystallographic alignment of the monolayers.

The work is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the Priority Programme SPP 2244 2DMP “Physics of van der Waal heterostructures” (project ID 443274823).

Light matter coupling with strong Berry curvature and quantum geometry

We study light-matter-interaction in quantum materials which are dominated by topological effects. For materials exhibiting dispersive bands with a narrow gap and strong spin-orbit coupling, the photon polarization couples to the Berry curvature of the Bloch states, whereas for materials exhibiting flat bands, the photon polarization couples to the quantum metric of the Bloch states. 

These quantum geometric properties become important in the context of many-body correlations, since, for example, they are thought to be key in understanding exotic phases, such as flat-band superconductivity.

To access these topological properties, we utilize a resonant mid-infrared excitation (4 µm – 18 µm) at the relevant interband energies, and we detect the optical selection rules by an electronic measurement.