Cooperative structural and Peierls transition of indium chains on Si(111)

We have performed high-resolution angle-resolved photoemission spectroscopy on quasi-one-dimensional indium chains on the Si(111) surface to study the temperature-induced metal-insulator (MI) transition accompanied by the $4\times 1$ to $8\times 2$ structural change. The band dispersion near $E_F$ shows an abrupt change at $120\mathrm{K}$, giving a relatively large energy gap compared to the energy scale of the transition temperature. The band dispersion of the $8\times 2$ phase shows no discernible temperature evolution, in sharp contrast to the conventional simple Peierls or structural transition. The experimental results suggest that the Peierls instability is important in the MI transition, while other structural effects are cooperatively involved.

Figure 1

(Color) ARPES intensity plot at $E_F$ $(E_F\pm 30\mathrm{meV})$ as a function of two-dimensional wave vector measured with $\mathrm{He}I\alpha$ resonance line at $295\mathrm{K}$. The inset shows the BZ of $\mathrm{Si}\left(111\right)1\times 1$ and $\mathrm{In}(4\times 1)$. Light blue arrows show the momentum region where the ARPES spectra in Fig. 3 are measured.

Figure 2

(Color) Band dispersion at various cuts shown in (c) at (a) $130\mathrm{K}$ and (b) $80\mathrm{K}$. (c) Location of cuts C–F in the BZ together with the minimum gap locus of band $m_2^{\prime }$ (red circles). The gray area corresponds to the Fermi surfaces $M_2$ and $M_3$. (d) Momentum dependence of the gap size for band $m_2^{\prime }$ determined by plotting the energy position of the peak at the minimum gap locus.

Figure 3

(Color) (a) and (b) Temperature dependence of band dispersions near $E_F$ measured along cuts A and B shown in Fig. 1. Dashed black lines at $T=295$ and $70\mathrm{K}$ show the position of each band determined by the peak position of the energy distribution curve (EDC). Red lines denote the regions where MDCs in Fig. 4 were measured. (c) Temperature dependence of EDC measured at the momentum location shown by a red arrow in (a). Black bars show the peak position of each spectrum.

Figure 4

(Color) (a)–(d) Temperature dependence of MDCs measured at locations shown by red lines in Figs. 3a, 3b. (e) Temperature dependence of normalized ARPES intensity for bands $m_2^{\prime }$ and $m_3^{\prime }$, and the normalized intensity loss for bands $m_2$ and $m_3$. Green circles show the ratio of $8\times 2$ area at various temperatures determined by STM (Ref. 17).