CiteULike: kas's Jiang

Band structure asymmetry of bilayer graphene revealed by infrared spectroscopy

ZQ Li — 2008-07-25T00:25:52-00:00

(24 Jul 2008)

We report on infrared spectroscopy of bilayer graphene integrated in gated structures. We observed a significant asymmetry in the optical conductivity upon electrostatic doping of electrons and holes. We show that this finding arises from a marked asymmetry between the valence and conduction bands, which is mainly due to the inequivalence of the two sublattices within the graphene layer. From the conductivity data, the energy difference of the two sublattices is determined.

Andreev conductance in the d + id[sup [prime]]-wave superconducting states of graphene

Yongjin Jiang — 2008-06-14T16:37:27-00:00

Physical Review B (Condensed Matter and Materials Physics), Vol. 77, No. 23. (2008)

We show that effective superconducting orders generally emerge at low energy in the superconducting state of graphene with conventionally defined pairing symmetry. We study a particular interesting example, the dx2−y2+idxy[prime]" align="middle"> spin singlet pairing state in graphene which can be generated by electronic correlation. We find that effectively the d+id-wave state is a state with mixed s-wave and exotic p+ip-wave pairing orders at low energy. This remarkable property leads to distinctive superconducting gap functions and behavior of the Andreev conductance spectra through a normal/superconducting graphene structure.

Raman and infrared properties and layer dependence of the phonon dispersions in multilayered graphene

Jin Jiang — 2008-06-14T16:35:11-00:00

Physical Review B (Condensed Matter and Materials Physics), Vol. 77, No. 23. (2008)

The symmetry group analysis is applied to classify the phonon modes of N-stacked graphene layers (NSGLs) with AB and AA stacking, particularly their infrared and Raman properties. The dispersions of various phonon modes are calculated in a multilayer vibrational model, which is generalized from the lattice vibrational potentials of graphene to including the interlayer interactions in NSGLs. The experimentally reported redshift phenomena in the layer-number dependence of the intralayer optical C-C stretching mode frequencies are interpreted. An interesting low-frequency interlayer optical mode is revealed to be Raman or infrared active in even or odd NSGLs, respectively. Its frequency shift is sensitive to the layer number and saturated at about 10 layers.

Graphene-Based Liquid Crystal Device

Peter Blake — 2008-05-18T19:21:36-00:00

Nano Lett. (30 April 2008)

Abstract: Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.

Cyclotron Resonance in Bilayer Graphene

EA Henriksen — 2008-05-16T12:13:28-00:00

Physical Review Letters, Vol. 100, No. 8. (2008)

We present the first measurements of cyclotron resonance of electrons and holes in bilayer graphene. In magnetic fields up to B=18 T, we observe four distinct intraband transitions in both the conduction and valence bands. The transition energies are roughly linear in B between the lowest Landau levels, whereas they follow for the higher transitions. This highly unusual behavior represents a change from a parabolic to a linear energy dispersion. The density of states derived from our data generally agrees with the existing lowest order tight binding calculation for bilayer graphene. However, in comparing data to theory, a single set of fitting parameters fails to describe the experimental results.