Phase transition of quasi-1D atomic chain on Pt/Ge(001) surface studied by reflection high-energy positron diffraction

Mochizuki, Izumi; Fukaya, Yuki   ; Maekawa, Masaki; Kawasuso, Atsuo; Wada, Ken*; Hyodo, Toshio*

Defect-free, single atomic, and quasi-one dimensional nanowires are formed on a Pt/Ge(001) surface. Using reflection high-energy positron diffraction (RHEPD), we have reported that the Nano-Wire (NW) model explains the fundamental structure of the observed nanowires. Recently, it has been reported that the nanowires undergo a Peierls transition below 80 K. We have studied about the phase transition phenomenon using RHEPD and angle resolved photoemission spectroscopy (ARPES). The RHEPD spot intensity of the one-beam rocking curve at RT increases compared to that at 35 K. According to the analysis with a dynamical diffraction theory, the change of the rocking curves implies the structural phase transition due to the height difference of the topmost Ge dimer atoms in the low-temperature phase, while that disappears in high-temperature. The ARPES results also show that the phase transition is caused by the concerted lattice distortion accompanying the formation of charge density waves.