Coexistence of Two Different Peierls Distortions within an Atomic Scale Wire: Si(553)-Au

The ground state property of a Au-induced atomic wire array on a stepped Si(553) surface with interesting 1D metallic bands was investigated. Electron diffraction and scanning tunneling microscopy reveal an intriguing coexistence of triple- and double-period lattice distortions at low temperature. Angle-resolved photoemission observes both the nearly $1/3$- and $1/2$-filled bands to gradually open energy gaps upon cooling. We explain these unusual findings as due to the occurrence of Peierls distortions of triple and double periods on the two different atomic-scale chain elements, respectively, within a single unit wire. The two Peierls distortions are suggested to have different transition temperatures and little lateral correlation between each other.

Figure 1

LEED patterns of Si(553)-Au at (a) 300, (b) 180, and (c) 70 K with an electron beam energy of 88 eV. (d) LEED intensity profiles along the wire direction ($k_{\parallel }$) at 300 and 70 K.

Figure 2

STM topographs of Si(553)-Au at (a) 300 and (b) 45 K for an area of $10\times 10{\mathrm{nm}}^2$ at 0.2 and 0.5 V biases (empty states), respectively. The ball and stick model in (a) shows the cross-sectional view of the unreconstructed Si(553) surface with steps and a narrow terrace.

Figure 3

(a) Schematics of the 1D metallic bands of Si(553)-Au along the wire direction ($k_{\parallel }$) [10, 13]. Experimental energy bands near the Fermi momentums [the shaded region in (a)] as measured by ARP at (b) 300 and (c) 70 K.

Figure 4

Temperature dependence (300 and 70 K) of the photoelectron EDC’s of (a) $S3$, (b) $S1$, and (c) $S2$, respectively, at the corresponding Fermi wave vectors. The arrows indicate the centers of the leading edges of the EDC’s. (d) More detailed temperature dependence of the energy gaps below $E_{\mathrm{F}}$ of $S3$ (solid circle), $S1$ (open circle), and $S2$ (dotted line). For $S1$ and $S3$, the temperature dependences $\Delta (T)$ are reasonably fitted with the Bardeen-Cooper-Schrieffer function for a relatively weak electron-phonon coupling, $\Delta (T)=\Delta (T=0)(1-T/T_{\mathrm{c}}{)}^{-1/2}$, with $T_c$ the transition temperature [23].