Robust Floquet-induced gap in irradiated graphite

TL;DR

This study demonstrates a persistent Floquet-induced electronic gap in bulk graphite under intense mid-infrared irradiation, revealing potential for light-controlled quantum phase engineering.

Contribution

It provides direct experimental evidence of a robust Floquet-induced gap in graphite, despite interlayer coupling and photo-excitation, advancing Floquet engineering in bulk materials.

Findings

Floquet-induced gaps observed at resonance points in valence and conduction bands.

Coexistence of gaps and photo-excited carriers with distinct timescales.

Graphite can serve as a platform for coherent manipulation of Dirac fermions.

Abstract

Floquet engineering provides an emerging pathway for tailoring the electronic states of quantum materials through time-periodic drive. A critical step along this direction is achieving light-induced modifications of the dynamical electronic structure, such as avoided-crossing gap at the Floquet Brillouin zone boundary, via efficient coupling of electrons with the coherent light-field. Here, we report robust Floquet-induced gap in bulk graphite that persists despite the presence of interlayer coupling and photo-excitation. Using time- and angle-resolved photoemission spectroscopy with intense mid-infrared pumping, we directly reveal Floquet-induced gaps at resonance points both in the valence and conduction bands, accompanied by coherent Floquet sidebands. The gap and sidebands coexist with photo-excited carriers, yet their distinct timescales allow us to disentangle their origins. Our demonstration of robust Floquet-induced gaps establishes graphite as a platform for coherent manipulation of Dirac fermions and realization of light-engineered quantum phases.