# Ultrafast topological phenomena in gapped graphene

## TL;DR

This paper investigates how a band gap in graphene induces topological resonances under strong optical pulses, leading to valley-selective electron populations and chiral textures, which vanish when the gap closes.

## Contribution

It demonstrates the direct link between the band gap and topological resonances in gapped graphene, revealing the emergence of valley-selective populations under strong optical excitation.

## Key findings

- Topological resonances are linked to the presence of a band gap.
- Valley-selective population occurs under strong chiral optical pulses.
- Chirality in electron distribution disappears as the band gap closes.

## Abstract

In the model of gapped graphene, we have shown how the recently predicted topological resonances are solely related to the presence of an energy band gap at the $K$ and $K^\prime$ points of the Brillouin zone. In the field of a strong single-oscillation chiral (circularly-polarized) optical pulse, the topological resonance causes the valley-selective population of the conduction band. This population distribution represents a chiral texture in the reciprocal space that is structured with respect to the pulse separatrix as has earlier been predicted for transition metal dichalcogenides. As the band gap is switched off, this chirality gradually disappears replaced by an achiral distribution characteristic of graphene.