Ultrafast Lightwave Engineering in 2D Materials

The discovery of two-dimensional (2D) graphene ignited a global surge in creating atomically thin materials with remarkable transport and optoelectronic properties -- key ingredients for next-generation technologies. In this talk, I will demonstrate how intense, tailored laser pulses can unlock functionalities in 2D materials that are otherwise forbidden by symmetry, enabling phenomena such as valley polarization and bulk photogalvanic currents even in inversion-symmetric systems.

I will first show how valley-selective excitation in gapless graphene can be achieved by all-optical means. By engineering laser waveforms to match the sublattice symmetry of graphene, it becomes possible to induce and probe valley polarization in a material long believed to be incompatible with light-driven valleytronics [1-3]. Building on this, I will present a fully coherent protocol that enables valley-selective excitation, de-excitation, and ultrafast switching between valleys within mere tens of femtoseconds -- well below typical valley decoherence times [4]. In the second part of the talk, I will introduce a new mechanism to achieve controllable valley polarization using a nonresonant, linearly polarized pulse, without relying on carrier-envelope-phase stabilization or multicolor fields. Finally, I will discuss an all-optical method to generate and control bulk photogalvanic currents in graphene and other 2D materials, opening pathways toward ultrafast valleytronics and on-chip light-driven electronics [5,6].