Infrared spectroscopy of electronic bands in bilayer graphene

Abstract

We present infrared spectra ͑0.1-1 eV͒ of electrostatically gated bilayer graphene as a function of doping and compare it with tight-binding calculations. All major spectral features corresponding to the expected interband transitions are identified in the spectra: a strong peak due to transitions between parallel split-off bands and two onset-like features due to transitions between valence and conduction bands. A strong gate voltage dependence of these structures and a significant electron-hole asymmetry are observed that we use to extract several band parameters. The structures related to the gate-induced band gap are less pronounced in the experiment than predicted by the tight-binding model that uses parameters obtained from previous experiments on graphite and recent self-consistent band-gap calculations.

The electronic properties of bilayer graphene

“…Thus, there are five independent parameters in the Hamiltonian (16) of intrinsic bilayer graphene, namely γ 0 , γ 1 , γ 3 , γ 4 and ∆ ′ . The band structure predicted by the tight-binding model has been compared to observations from photoemission [16], Raman [76] and infrared spectroscopy [55,56,[78][79][80][81]. Parameter values determined by fitting to experiments are listed in Table I for bulk graphite [67], for bilayer graphene by Raman [76,77] and infrared [55,56,80] spectroscopy, and for a This parameter was not determined by the given experiment, the value quoted was taken from previous literature.…”

“…The electronic structure of bilayer graphene was probed by spectroscopic measurements in zero magnetic field [16,55,56,79,80,129,130], and also in high magnetic fields [78]. The optical absorption for perpendicularly incident light is described by the dynamical conductivity in a electric field parallel to the layers, in both symmetric bilayers [164,[226][227][228] and in the presence of an interlayer-asymmetry gap [227] For symmetric bilayer graphene, this is explicitly estimated as [164,[226][227][228] Re σ xx (ω) = g v g s 16…”

Tunneling Plasmonics in Bilayer Graphene

“…However, electrostatic tuning of graphene is readily attainable in gated structures. Through back-gating, we were able to explore the key aspects of tunneling plasmonics on bilayer graphene plasmons by tuning both the Fermi energy as well as interlayer doping asymmetry 16,18,19 . In Figure 2, we show a selected dataset of gate-dependent near-field images of a graphene sample containing both single-layer and bilayer graphene.…”

Transport in gapped bilayer graphene: The role of potential fluctuations

“…A perpendicular electric field breaks the inversion symmetry between the two graphene layers and results in a field-dependent bandgap 1-3 . Its experimental signatures have been observed by infrared spectroscopy [4][5][6][7] and angle-resolved photoemission 8 , but remain incomplete and perplexing in transport [9][10][11][12] . Near room temperature, Xia et al observes thermally activated conduction and attributes it to Schottky barriers at the electrode-gapped bilayer interface 11 .…”