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

Restructure science in South Korea

A switch to projects led by independent principal investigators would build on the success of the nation's centralized research agenda, urges Han Woong Yeom. © 2018 Nature.11Ysciescopu

Atomistic origin of metal versus charge-density-wave phase separation in indium atomic wires on Si(111)

We investigate in atomic scale the electronic phase separation occurring in the well known quasi 1D charge-density wave (CDW) phase of the In atomic wire array on a Si(111) surface. The characteristic atomic scale defects, originated from excess In atoms, are found to be actively involved in the formation of the phase boundary between the metallic and the CDW phases by extensive analysis of scanning tunneling microscopy images at various temperatures. These particular defects flip the phase of the quasi 1D CDW to impose strong local constraints in the CDW correlation. We show that such local constraints and the substantial interwire CDW interaction induce local condensates of CDW and the phase separation between the metallic and the CDW phases. This work unveils the atomistic origin of the electronic phase separation, highlighting the importance of atomic scale structures of defects and their collective interaction in electronically inhomogeneous materials

Interfacial Engineering of Flexible Transparent Conducting Films

One-dimensional (1D) carbon nanotubes (CNTs) and silver nanowires (AgNWs) have been used as replacements for brittle indium tin oxide (ITO) in the fabrication of transparent conducting films (TCFs), which can be used in opto-electronic devices such as screen panels, solar cell panels, and organic light-emitting diodes. This chapter describes a fabrication method of high-performance TCFs by solution processing of single-walled CNTs (SWCNTs) and AgNWs. Highly uniform TCFs with SWCNTs and AgNW inks were fabricated using spray deposition. Their performance was modulated by interfacial engineering such as overcoating with silane compound for densification of SWCNT networks and chemical or photothermal welding of SWCNT networks on thermoplastic substrates. Moreover, the hybridization of SWCNTs, AgNWs, and graphene oxide nanosheets is a promising approach to mitigate their drawbacks via p-type doping, electrical stabilization, or interfacial stabilization on plastic substrates. The rational control of 1D material networks can provide a good opportunity to fabricate high-performance TCFs for flexible opto-electronic devices