Direct observation of Floquet-Bloch states in monolayer graphene

Abstract

Floquet engineering is a novel method of manipulating quantum phases of matter via periodic driving [1, 2]. It has successfully been utilized in different platforms ranging from photonic systems [3] to optical lattice of ultracold atoms [4, 5]. In solids, light can be used as the periodic drive via coherent light-matter interaction. This leads to hybridization of Bloch electrons with photons resulting in replica bands known as Floquet-Bloch states. After the direct observation of Floquet-Bloch states in a topological insulator [6], their manifestations have been seen in a number of other experiments [7-14]. By engineering the electronic band structure using Floquet-Bloch states, various exotic phase transitions have been predicted [15-22] to occur. To realize these phases, it is necessary to better understand the nature of Floquet-Bloch states in different materials. However, direct energy and momentum resolved observation of these states is still limited to only few material systems [6, 10, 14, 23, 24]. Here, we report direct observation of Floquet-Bloch states in monolayer epitaxial graphene which was the first proposed material platform [15] for Floquet engineering. By using time- and angle-resolved photoemission spectroscopy (trARPES) with mid-infrared (mid-IR) pump excitation, we detected replicas of the Dirac cone. Pump polarization dependence of these replica bands unequivocally shows that they originate from the scattering between Floquet-Bloch states and photon-dressed free-electron-like photoemission final states, called Volkov states. Beyond graphene, our method can potentially be used to directly observe Floquet-Bloch states in other systems paving the way for Floquet engineering in a wide range of quantum materials.

References in corpus (8)

• Photovoltaic Hall effect in graphene
• Tuning laser-induced bandgaps in graphene
• Pseudospin-selective Floquet band engineering in black phosphorus
• Optical response of graphene under intense terahertz fields
• Effect of radiation on transport in graphene
• Buildup and dephasing of Floquet-Bloch bands on subcycle time scales
• Phonon driven Floquet matter
• Floquet engineering of black phosphorus upon below-gap pumping

Cited by in corpus (21)

• Observation of Floquet states in graphene
• Observation of Floquet-induced gap in graphene
• Floquet optical selection rules in black phosphorus
• The Streda Formula for Floquet Systems: Topological Invariants and Quantized Anomalies from Cesaro Summation
• Light-induced Floquet spin-triplet Cooper pairs in unconventional magnets
• Quantum control of Hubbard excitons
• Flat bands in condensed-matter systems -- perspective for magnetism and superconductivity
• Asymmetry-induced radiative heat transfer in Floquet systems
• Quantum transport phenomena induced by time-dependent fields
• Monolayer transition metal dichalcogenides under finite-pulse polarized radiation
• All-optical band structure reconstruction and onset of Landau quantization of Dirac fermions
• Stability of Floquet sidebands and quantum coherence in 1D strongly interacting spinless fermions
• Robust purely optical signatures of Floquet states in laser-dressed crystals
• Floquet-Engineering Weyl Points and Linked Fermi Arcs from Straight Nodal Lines
• Lippmann-Schwinger Approach for Accurate Photoelectron Wavefunctions and Angle-Resolved Photoemission Spectra from First Principles
• Emergent Weyl-like points in periodically modulated systems
• Occupation Dynamics of Floquet-Volkov States and Spectral Sum Rule
• Nonequilibrium hysteretic phase transitions in periodically light-driven superconductors
• Floquet second-order topological insulator in strained graphene
• $SU(N)$ spin-phonon simulations of Floquet dynamics in spin $S>1/2$ Mott insulators
• Dielectric Screening in Electromagnetic Dressing of Semiconductors