We reveal a giant Rashba effect (α_R≈1.3  eV Å) on a surface state of Ir(111) by angle-resolved photoemission and by density functional theory. It is demonstrated that the existence of the surface state, its spin polarization, and the size of its Rashba-type spin-orbit splitting remain unaffected whe...

[Phys. Rev. Lett. 108, 066804] Published Thu Feb 09, 2012

The experimentally observed metal-to-insulator transition in hydrogenated graphene is numerically confirmed for actual sized graphene samples and realistic impurity concentrations. The eigenstates of our tight-binding model with substitutional disorder corroborate the formation of electron-hole pudd...

[Phys. Rev. Lett. 108, 066402] Published Thu Feb 09, 2012

Through a systematic structural search we found an allotrope of carbon with Cmmm symmetry which we predict to be more stable than graphite for pressures above 10 GPa. This material, which we refer to as Z-carbon, is formed by pure sp³ bonds and it provides an explanation to several features in exper...

[Phys. Rev. Lett. 108, 065501] Published Tue Feb 07, 2012

Within an effective Dirac theory the low-energy dispersions of monolayer graphene in the presence of Rashba spin-orbit coupling and spin-degenerate bilayer graphene are described by formally identical expressions. We explore implications of this correspondence for transport by choosing chiral tunnel...

[Phys. Rev. B 85, 085406] Published Fri Feb 03, 2012

First-principles electronic structure calculations based on spin-polarized density functional theory were carried out to study the adsorption of oxygen-containing functional groups -OH, -CHO, and -COOH on a two-dimensional (2D) infinite graphene sheet without edge states and defects. We find that th...

[Phys. Rev. B 85, 085404] Published Fri Feb 03, 2012

Based on first-principles calculations, we predict that 5d transition metals on graphene present a unique class of hybrid systems exhibiting topological transport effects that can be manipulated effectively by external electric fields. The origin of this phenomenon lies in the exceptional magnetic p...

[Phys. Rev. Lett. 108, 056802] Published Wed Feb 01, 2012

The unoccupied electronic states of epitaxially grown graphene on Ru(0001) have been explored by time- and angle-resolved two-photon photoemission. We identify a Ru derived resonance and a Ru/graphene interface state at 0.91 and 2.58 eV above the Fermi level, as well as three image-potential derived...

[Phys. Rev. Lett. 108, 056801] Published Tue Jan 31, 2012

We demonstrate that 100% light absorption can take place in a single patterned sheet of doped graphene. General analysis shows that a planar array of small particles with losses exhibits full absorption under critical-coupling conditions provided the cross section of each individual particle is comp...

[Phys. Rev. Lett. 108, 047401] Published Fri Jan 27, 2012

We identify by ab initio calculations an orthorhombic carbon (O-carbon) in Pbam (D_2h⁹) symmetry for compressed graphite in AA stacking, which is formed via a distinct one-layer by one-layer slip and buckling mechanism along the [210] direction. It is dynamically stable and energetically more favorab...

[Phys. Rev. B 85, 033410] Published Fri Jan 27, 2012

Electronic structures and scanning tunneling microscopy (STM) patterns of boron- and nitrogen-doped bilayer graphene are predicted using state-of-the-art first-principles calculations. Asymmetric doping is considered, leading to different charge-carrier densities on each graphene layer and to a band...

[Phys. Rev. B 85, 035444] Published Fri Jan 27, 2012

There is a growing need to understand the mechanical and electronic properties of nonideal graphene nanoribbons. Using objective molecular dynamics and a density-functional-based tight-binding model, we investigate the effects of torsion on the electromechanical properties of graphene nanoribbons wi...

[Phys. Rev. B 85, 035445] Published Fri Jan 27, 2012

We report, within a picosecond time scale, fast relaxation and relatively slow recombination dynamics of photogenerated electrons and holes in an exfoliated graphene under infrared pulse excitation. We conduct time-domain spectroscopic studies using an optical pump and terahertz probe with an optica...

[Phys. Rev. B 85, 035443] Published Thu Jan 26, 2012

We report on the observation of enhanced high harmonics from a carbon plasma using sub-5-fs laser pulses. The efficiency of harmonic generation in the range of 14–25 eV was up to five times higher in the case of a plasma medium (graphite ablation) compared with gas (argon) under similar experimental...

[Phys. Rev. A 85, 015807] Published Thu Jan 26, 2012

Motivated by a recent photochlorination experiment [ B. Li et al. ACS Nano 5 5957 (2011)], we study theoretically the interaction of chlorine with graphene. In previous theoretical studies, covalent binding between chlorine and carbon atoms has been elusive upon adsorption to the graphene basal pla...

[Phys. Rev. B 85, 035440] Published Wed Jan 25, 2012

We analyze the influence of biaxial strain on the double-resonance (D and 2D) Raman bands of graphite-related materials. A substantial nonlinear dependence of these bands with the strain is observed, evidencing a quite different effect on the electronic structure around the K and Γ points of the fir...

[Phys. Rev. B 85, 033407] Published Tue Jan 24, 2012

Using low-temperature scanning tunneling spectroscopy, we map the local density of states of graphene quantum dots supported on Ir(111). Because of a band gap in the projected Ir band structure around the graphene K point, the electronic properties of the QDs are dominantly graphenelike. Indeed, we ...

[Phys. Rev. Lett. 108, 046801] Published Mon Jan 23, 2012

We present a theory for the lattice thermal conductivity κ_L of single-walled boron nitride nanotubes (BNNTs) and multilayer hexagonal boron nitride (MLBN), which is based on an exact numerical solution of the phonon Boltzmann equation. Coupling between layers in MLBN and nanotube curvature in BNNTs ...

[Phys. Rev. B 85, 035436] Published Mon Jan 23, 2012

We investigate the transduction of motion from a nanomechanical resonator to the cantilever/tip probe of an atomic force microscope. Our results show that amplitude-modulated high-frequency vibrations of nanomechanical resonators can be measured by means of a low-resonance frequency cantilever as a ...

[Phys. Rev. B 85, 035433] Published Fri Jan 20, 2012

Using a first-principle plane-wave method we investigate the effects of static charging on the structural, electronic, and magnetic properties of suspended, single-layer graphene, graphane, fluorographene, BN, and MoS₂ in a honeycomb structure. The limitations of periodic boundary conditions in the ...

[Phys. Rev. B 85, 045121] Published Fri Jan 20, 2012

By thermally cycling single layer graphene in air, we observe irreversible upshifts of the Raman G and 2D bands of 24 and 23 cm⁻¹, respectively. These upshifts are attributed to an in-plane compression of the graphene induced by the mismatch of thermal expansion coefficients between the graphene and...

[Phys. Rev. B 85, 035431] Published Fri Jan 20, 2012

Building a high-quality trilayer graphene sheet into a dual-gate field-effect transistor and measuring its electronic properties, three physicists from California Institute of Technology reveal a number of new findings about the trilayer graphene, which includes a sequence of quantum Hall plateaus seen for the first time.

[Phys. Rev. X 2, 011004] Published Thu Jan 19, 2012

In this paper, the exact solutions of Dirac electronic states of graphene in Coulomb and magnetic fields are acquired. The Coulomb field not only causes the splitting of Landau levels in gapless graphene but also leads to the variation of the energy level ordering in gapped graphene. The dependence ...

[Phys. Rev. B 85, 035429] Published Thu Jan 19, 2012

Being a semimetal, pure monolayer graphene cannot be used directly in devices which rely on controlled and reliable transistor operations. Substitutional doping of graphene by nitrogen at macroscopic concentrations is predicted to create two monolayer compounds that are both stable and semiconducting with sizable band gaps.

[Phys. Rev. X 2, 011003] Published Wed Jan 18, 2012

The principal structural defects in graphene layers, synthesized on a carbon-terminated face, i.e., the SiC(0001̅ ) face of a 4H-SiC substrate, are investigated using microscopic methods. Results of high-resolution transmission electron microscopy (HRTEM) reveal their atomic arrangement. The ...

[Phys. Rev. B 85, 045426] Published Wed Jan 18, 2012

Diodes based on metal-semiconductor interfaces are common place in semiconductor electronics. What happens when the normal metal is replaced by monolayer graphene? A group of physicists at University of Florida experimentally demonstrate that graphene-semiconductor interfaces make interesting diodes for a surprisingly wide variety of semiconductors.

[Phys. Rev. X 2, 011002] Published Tue Jan 17, 2012

First-principles calculations of substitutional defects and vacancies are performed for zigzag-edged hybrid C/BN nanosheets and nanotubes which recently have been proposed to exhibit half-metallic properties. The formation energies show that defects form preferentially at the interfaces between grap...

[Phys. Rev. B 85, 045422] Published Tue Jan 17, 2012

Recent studies show that the electronic structures of graphene can be modified by strain, and it was predicted that strain in graphene can induce peaks in the local density of states (LDOS), mimicking Landau levels (LLs) generated in the presence of a large magnetic field. Here we report the scannin...

[Phys. Rev. B 85, 035422] Published Tue Jan 17, 2012

We show that for impacting argon clusters, both mean projected ranges of the constituents and depths of radiation damage in diamond scale linearly with momentum. The same dependence was earlier found for keV-energy cluster implantation in graphite, thus suggesting the universality of this scaling la...

[Phys. Rev. B 85, 033405] Published Tue Jan 17, 2012

By performing the first-principles simulation of electron-ion dynamics based on the time-dependent density-functional theory, we propose a way to produce graphene from graphene oxides by means of the laser-induced reduction without using chemical species. Epoxy and hydroxyl groups on graphene sheets...

[Phys. Rev. B 85, 033402] Published Tue Jan 17, 2012

Graphene films prepared by heating the SiC(0001̅ ) surface (the C-face of the {0001} surfaces) in a vacuum or in a Si-rich environment are compared. It is found that different interface structures occur for the two situations. The former yields a well known 3 × 3 reconstructed interface, wher...

[Phys. Rev. B 85, 041404] Published Fri Jan 13, 2012