Topological Solitons versus Nonsolitonic Phase Defects in a Quasi-One-Dimensional Charge-Density Wave

We investigated phase defects in a quasi-one-dimensional commensurate charge-density wave (CDW) system, an In atomic wire array on Si(111), using low temperature scanning tunneling microscopy. The unique fourfold degeneracy of the CDW state leads to various phase defects, among which intrinsic solitons are clearly distinguished. The solitons exhibit a characteristic variation of the CDW amplitude with a coherence length of about 4 nm, as expected from the electronic structure, and a localized electronic state within the CDW gap. While most of the observed solitons are trapped by extrinsic defects, moving solitons are also identified and their novel interaction with extrinsic defects is disclosed. DOI: 10.1103/PhysRevLett.109.246802X1115sciescopu

Radial Band Structure of Electrons in Liquid Metals

The electronic band structure of a liquid metal was investigated by measuring precisely the evolution of angle-resolved photoelectron spectra during the melting of a Pb monolayer on a Si(111) surface. We found that the liquid monolayer exhibits a free-electron-like band and it undergoes a coherent radial scattering, imposed by the radial correlation of constituent atoms, to form a characteristic secondary hole band. This unique double radial bands and their gradual evolution during melting can be quantitatively reproduced, including detailed spectral intensity profiles, with our radial scattering model based on a theoretical prediction of 1962. Our result establishes the radial band structure as a key concept for describing the nature of electrons in strongly disordered states of matter.Comment: 4 pages, 4 figures, accepted to Physical Review Letter

THE POTENTIAL OF HYDROLYZED URINE AS A SOLVENT FOR BIOGAS UPGRADING

Department of Urban and Environmental Engineering (Environmental Science and Engineering )Currently, global warming is accelerating and greenhouse gases are known to be the main cause. Therefore, various studies on the reduction of greenhouse gases have been carried out in order to solve global warming around the world. The purpose of this study is to separate carbon dioxide and methane from biogas in anaerobic digesters to reduce carbon dioxide, which accounts for a large proportion of greenhouse gases. As a criterion for selecting a suitable solvent, not only the reduction of carbon dioxide but also the recycling of collected carbon dioxide was also observed. This study on the solvent which plays a dominant role in the physical interaction rather than the chemical interaction with the carbon dioxide enables us to improve the reuse efficiency of the solvent through the increase and decrease of the pressure. In order to find a suitable solvent for the purpose of the experiment, the solvent was divided into five categories. Water was used as a basic comparison of the experiments and pure solvents were used to increase the dissolved amount of carbon dioxide. We also used an aqueous solution of artificial seawater with salt added to the water to determine how salt influences the degassing of the anaerobic digestion gas (AD gas). The aqueous solution was used to confirm the synergy effect between water and solvent. Finally, the experiment was carried out by mixing acetone-based solutions with various advantages in pure solvent form. To maximize the merits of each solvent, we have combined three tertiary systems: water with the advantage of increasing the rate of carbon dioxide degassing, salt that can lead to a salting out effect, and acetone, which can increase the solubility of carbon dioxide. Compared with other experimental conditions in the tertiary system, it was possible to capture a high rate of carbon dioxide in the degassed AD gas with increasing solubility of carbon dioxide. It is concluded that the tertiary system is the best condition for the experimental purpose in the case of containing a small amount of water.clos

Visualizing Atomic-Scale Negative Differential Resistance in Bilayer Graphene

We investigate the atomic-scale tunneling characteristics of bilayer graphene on silicon carbide using the scanning tunneling microscopy. The high-resolution tunneling spectroscopy reveals an unexpected negative differential resistance (NDR) at the Dirac energy, which spatially varies within the single unit cell of bilayer graphene. The origin of NDR is explained by two near-gap van Hove singularities emerging in the electronic spectrum of bilayer graphene under a transverse electric field, which are strongly localized on two sublattices in different layers. Furthermore, defects near the tunneling contact are found to strongly impact on NDR through the electron interference. Our result provides an atomic-level understanding of quantum tunneling in bilayer graphene, and constitutes a useful step towards graphene-based tunneling devices. DOI: 10.1103/PhysRevLett.110.036804X11109sciescopu