A system with a complex phase transition: Indium chains on Si(111)
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We examined in detail the geometric and electronic structure of thin In chains on vicinal Si(111) surfaces by means of low energy electron diffraction and ultrahigh-resolution photoemission as a function of temperature. Our data reveal a transition around Tc = 115 K from a high temperature ( 4×1)- to a low temperature ( 8×2)-phase being reversible with a small hysteresis of the order 10 K. ARPES spectra exhibit clearly important concomitant changes in the electronic band structure near the Fermi surfaces and at the border of the surface Brillouin zones. We derive the dispersive behavior of the bands involved in the transition in detail and demonstrate that at least two surface state bands m2 and m3 show the opening of a pseudo energy gap on the Fermi surface leaving small but finite spectral weight in the low-temperature state. We conclude that this transition is probably driven by a similar but more complex mechanism than in a conventional Peierls transition.
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