Han Woong Yeom

Self-assembled indium linear chains on the Si(111) surface are found to exhibit instability of the metallic phase and 1D charge density wave (CDW). The room-temperature metallic phase of these chains undergoes a temperature-induced, reversible transition into a semiconducting phase. The 1D CDW along the chains is observed directly in real space by scanning tunneling microscopy at low temperature. The Fermi contours of the metallic phase measured by angle-resolved photoemission exhibit a perfect

The phase transition of a metallic In chain structure on Si(111) was investigated by high-resolution photoemission. Core-level spectra clearly elucidate that the symmetry breaking at low temperature occurs only within the inner parts of the In chains. In the valence bands, the transition is accompanied by the formation of pseudogaps of 80--150 meV and the band backfolding with only marginal changes of the band dispersion. No sign of Luttinger liquid behavior is observed in the spectral function

Angle-resolved photoemission (ARP) is employed to investigate the electronic structure of an extremely anisotropic form of nanocrystals--GdSi(2-x) nanowires on Si(100). Using a stepped Si(100) surface, a well-ordered and uniformly oriented array of nanowires is formed along the step edges as confirmed by diffraction and microscopy. The ARP measurement discloses two distinct electronic bands near the Fermi level, which disperse one dimensionally along the nanowires. These bands are metallic with

The submonolayer oxygen adsorption on the Si(001) surface is studied by high-resolution Si $2p$ photoemission. Significant intensities of Si $2p$ components due to the ${\mathrm{Si}}^{2+}$ and ${\mathrm{Si}}^{3+}$ species are observed from the very early stage of adsorption at 120 K, which grow linearly with the oxygen coverage. This indicates an active agglomeration of oxygen adsorbates even for submonolayer adsorption at low temperatures. Annealing above \ensuremath{\sim}500 K of oxygen adlaye

Nonvanishing Berry curvature dipole (BCD) and persistent spin texture (PST) are intriguing physical manifestations of electronic states in noncentrosymmetric 2D materials. The former induces a nonlinear Hall conductivity while the latter offers a coherent spin current. Based on density-functional-theory (DFT) calculations, we demonstrate the coexistence of both phenomena in a Bi(110) monolayer with a distorted phosphorene structure. Both effects are concurrently enhanced due to the strong spin-o

The Si(557) surface with Au adsorbates consists of a well ordered array of atomic chains, which exhibit interesting one-dimensional (1D) metallic band structure with two nearly half-filled 1D bands. This system was recently found to undergo a metal-insulator transition below room temperature [Phys. Rev. Lett. 91, 196403 (2003)]. The structural and electronic changes upon the phase transition have been investigated in detail using scanning tunneling microscopy and spectroscopy (STM/STS) with the