Moiré superlattice materials

The electronic flat bands of moiré superlattices in 2D van-der-Waal’s (vdW) heterostructures, such as magic angle twisted bilayer graphene (1, 2) and WS2/WSe2 heterostructures (3, 4), favor a dominant role of electronic interactions and provide a rich domain to explore a variety of resulting electronic ground states such as superconductivity or correlated, Chern and Mott insulators. The vast amount of materials at hand (>1000) that can be potentially integrated into vdW heterostructures (5), presents an an exciting and almost fully unexplored research avenue to study the physics of correlated and topological low-dimensional quantum matters,

One major focus of our research activities is to investigate the microscopic nature of the electronic interactions and their interplay with topology in these systems, by combining scanning tunneling microscopy (STM) and transport experiments (6). We will apply advanced imaging techniques with an STM, such as Josephson STM and spin-polarized STM, in order to visualize the emergence superconducting and magnetic order parameters in these systems and to probe the response of these strongly correlated states to perturbations on the single atomic impurity level. For this purpose, we are currently designing state-of-the-art low-temperature STM instrumentation, specifically suited to the challenging nature of these experiments. 

(1) Y. Cao et al., Nature 556, 43-50 (2018)
(2) Y. Cao et al., Nature 556, 80-84 (2018)
(3) E.C. Reagan et al., Nature 579, 359–363 (2020)
(4) Y. Tang et al., Nature 579, 353-358 (2020)
(5) N. Mounet et al., Nature Nanotechnol. 13, 246-252 (2018)
(6) Y. Xie, B. Lian, B. Jäck et al., Nature 572, 101–105 (2019)