A 1D metallic surface state was created on an anisotropic InSb(001) surface covered with Bi. Angle-resolved photoelectron spectroscopy (ARPES) showed a 1D Fermi contour with almost no 2D distortion. Close to the Fermi level ($E_{rm F}$), the angle-in
tegrated photoelectron spectra showed power-law scaling with the binding energy and temperature. The ARPES plot above $E_{rm F}$ obtained thanks to thermally broadened Fermi edge at room temperature showed a 1D state with continuous metallic dispersion across $E_{rm F}$ and power-law intensity suppression around $E_{rm F}$. These results strongly suggest a Tomonaga-Luttinger liquid on the Bi/InSb(001) surface.
Spin-split two-dimensional electronic states have been observed on ultrathin Sn(001) films grown on InSb(001) substrates. Angle-resolved photoelectron spectroscopy (ARPES) performed on these films revealed Dirac-cone-like linear dispersion around the
$bar{Gamma}$ point of surface Brillouin zone, suggesting nearly massless electrons belonging to 2D surface states. The states disperse across a bandgap between bulk-like quantum well states in the films. Moreover, both circular dichroism of ARPES and spin-resolved ARPES studies show helical spin polarization of the Dirac-cone-like surface states, suggesting a topologically protected character as in a bulk topological insulator (TI). These results indicate that a quasi-3D TI phase can be realized in ultrathin films of zero-gap semiconductors.
We performed angle-resolved photoelectron spectroscopy of the Bi(111) surface to demonstrate that this surface support edge states of non-trivial topology. Along the $bar{Gamma}bar{M}$-direction of the surface Brillouin zone, a surface-state band dis
perses from the projected bulk valence bands at $bar{Gamma}$ to the conduction bands at $bar{M}$ continuously, indicating the non-trivial topological order of three-dimensional Bi bands. We ascribe this finding to the absence of band inversion at the $L$ point of the bulk Bi Brillouin zone. According to our analysis, a modification of tight-binding parameters can account for the non-trivial band structure of Bi without any other significant change on other physical properties.
