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Observation of Floquet-induced gap in graphene
Fei Wang1,2, Xuanxi Cai1,2, Xiao Tang1,2
1Department of Physics, Tsinghua University, Beijing, People's Republic of China.
Nature Materials
|March 24, 2026
Summary
Scientists observed a light-induced gap in graphene, a key signature of Floquet engineering. This breakthrough demonstrates control over electronic properties in graphene using light fields, paving the way for new quantum materials.
Area of Science:
- Condensed Matter Physics
- Quantum Materials Science
- Photonics
Background:
- Floquet engineering enables creating novel non-equilibrium phases of matter via time-periodic driving.
- Graphene served as the theoretical prototype for Floquet topological insulators, predicting a light-induced anomalous Hall effect.
- The key experimental signature, a hybridization gap at Floquet band crossings, remained unobserved in graphene.
Purpose of the Study:
- To experimentally observe the elusive Floquet-induced hybridization gap in monolayer graphene.
- To demonstrate Floquet band engineering in graphene using resonant light fields.
- To explore the properties and tunability of the observed gap.
Main Methods:
- Utilizing time- and angle-resolved photoemission spectroscopy (TR-MOKE).
- Subjecting monolayer graphene to resonant driving by a strong light field.
- Analyzing the spectroscopic signatures, including band crossings and sidebands.
Main Results:
- Direct observation of a Floquet-induced hybridization gap at Floquet band crossings in graphene.
- Coherent Floquet sidebands accompanying the gap opening.
- The gap exhibits momentum anisotropy and is tunable by light polarization, featuring two symmetry-protected Dirac nodes.
Conclusions:
- Provides the first experimental demonstration of Floquet band engineering in graphene.
- Confirms the existence of light-induced hybridization gaps as predicted.
- Opens avenues for creating novel light-field-engineered quantum phases in graphene and related 2D materials.
