Phys.org April 15, 2024
The stacking and twisting of atom-thin structures with matching crystal symmetry has provided a unique way to create new superlattice structures in which new properties emerge. An international team of researchers (Germany, Spain, USA – SLAC National Accelerator Laboratory, Stanford University) demonstrated a tailored light-wave-driven analogue to twisted layer stacking. Tailoring the spatial symmetry of the light waveform to that of the lattice of a hexagonal boron nitride monolayer and then twisting this waveform resulted in optical control of time-reversal symmetry breaking and the realization of the topological Haldane model in a laser-dressed two-dimensional insulating crystal. The parameters of the effective Haldane-type Hamiltonian could be controlled by rotating the light waveform enabling ultrafast switching between band structure configurations and allowing unprecedented control over the magnitude, location, and curvature of the bandgap leading to a measurable valley Hall current. According to the researchers the universality and robustness of their scheme paves the way to valley-selective bandgap engineering on the fly and unlocks the possibility of creating few-femtosecond switches with quantum degrees of freedom… read more. Open Access TECHNICAL ARTICLE
Comparison between experimental and theoretical results. Credit: Nature, April 15, 2024Â