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 controllability over strongly correlated electronic states promises unique electronic devices. A recent example is an optically induced ultrafast switching device based on the transition between the correlated Mott insulating state and a metallic state of a transition metal dichalcogenide 1T-TaS2. However, the electronic switching has been challenging and the nature of the transition has been veiled. Here we demonstrate the nanoscale electronic manipulation of the Mott state of 1T-TaS2. The

Chiral edge states are the hallmark of two- and three-dimensional topological materials, but their one-dimensional (1D) analog has not yet been found. We report that the 1D topological edge states, solitons, of the charge density wave system of indium atomic wires self-assembled on a silicon surface have chirality. The system is described by a coupled double Peierls-dimerized atomic chain, where the interchain coupling induces dynamical sublattice symmetry breaking. This changes its topological

Abstract Domain walls in interacting electronic systems can have distinct localized states, which often govern physical properties and may lead to unprecedented functionalities and novel devices. However, electronic states within domain walls themselves have not been clearly identified and understood for strongly correlated electron systems. Here, we resolve the electronic states localized on domain walls in a Mott-charge-density-wave insulator 1 T -TaS 2 using scanning tunneling spectroscopy. W

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

Abstract When two periodic potentials compete in materials, one may adopt the other, which straightforwardly generates topological defects. Of particular interest are domain walls in charge-, dipole-, and spin-ordered systems, which govern macroscopic properties and important functionality. However, detailed atomic and electronic structures of domain walls have often been uncertain and the microscopic mechanism of their functionality has been elusive. Here, we clarify the complete atomic and ele

High Resolution Image Download MS PowerPoint Slide 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

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

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

The atomic structure of the $c(2\ifmmode\times\else\texttimes\fi{}2)$ reconstruction of the $C$-terminated $3C\ensuremath{-}\mathrm{SiC}(001)$ surface was unambiguously determined by scanning tunneling microscopy and surface-core-level-resolved photoelectron diffraction studies. This surface is found to uniquely and uniformly consist of anomalous bridge-bonded C dimers with a C-C bond length of 1.22 \AA{}. Furthermore, an extensive angle-resolved photoemission study clearly identifies two occupi

Angle-resolved photoelectron spectroscopy (ARPES) using synchrotron radiation was employed to study the electronic structure of a well-ordered single-domain Si(001)2\ifmmode\times\else\texttimes\fi{}2-In surface. The existence of five surface state bands, denoted as ${S}_{1}$, ${S}_{2}$, ${S}_{2}^{\ensuremath{'}}$, ${S}_{3}$, and ${S}_{3}^{\ensuremath{'}}$ is revealed within the bulk band gap between 0.6 and 2.2 eV in binding energy (${E}_{B}$). The dispersions of these surface states are determ