Moiré lattices in space and time: engineering quantum matter

• Applicant: Dr. Urban Seifert
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544397233

Moiré lattices emerge as interference patterns when superposing periodic lattices with a small relative twist, or with mismatched lattice constants. Real-space unit cells of such moiré lattices can be orders-of-magnitude larger than in atomic solids, and electronic energy scales typically become quenched. As recent experiments on graphene and transition metal dichalcogenide (TMD) moiré heterostructures impressively demonstrate, such systems are highly versatile platforms for engineering (rather than discovering) quantum states of matter, offering an unprecedented degree of experimental control. At the same time, large length scales and quenched energy scales imply that driven moiré heterostructures are an excellent venue for studying non-equilibrium phenomena of strongly driven correlated-electron systems, since moderate field strengths are sufficient for achieving strong light-matter couplings in these systems. This may pave the way for the targeted stabilization of novel transient states with desired properties by means of optical driving. It is the key goal of this proposal to capitalize on the unique opportunities afforded by moiré lattice engineering. We will study new pathways for realizing and controlling quantum matter in such systems, both in equilibrium as well as in driven heterostructures. Our work is organized into two research lines: A. Space – We will study heterostructures of intrinsically correlated layers, in particular magnet-superconductor systems and of strongly fluctuating quantum magnets. These are markedly different from moiré heterostructures of weakly-interacting graphene/TMD layers and necessitate advanced theoretical modelling. Here, a particularly interesting common motif consists in gapless (and/or fractionalized) degrees of freedom which may emerge at moiré-stacking-induced domain walls. B. Time – We will be concerned with the out-of-equilibrium physics of driven moiré TMD systems. This includes pump-probe spectroscopy of interaction-driven orders, and we will study how multifrequency driving protocols can be used to dynamically stabilize highly-sought-after quantum spin liquid states in emergent Mott-insulating states of moiré TMD. Given that moiré heterostructures can be mechanically manipulated, we will further explore completely new means of mechanical driving such systems. The proposed project therefore offers a unified view on moiré lattices both in space and time, and resulting novel opportunities for engineering and controlling quantum matter.

• DFG Programme: Independent Junior Research Groups