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Seminar
FIELD Comp.Sciences:Nano Science
DATE March 15 (Fri), 2019
TIME 14:00-17:00
PLACE 1424
SPEAKER 김한철
HOST Kim, Hyun-Jung
INSTITUTE 숙명여자대학교
TITLE Solitons in a Quasi-One-Dimensional Charge-Density-Wave System: Si(111)In-8×2
ABSTRACT Metal adsorbed semiconductors have attracted much interest in surface science because they provide useful platforms to study exotic low-dimensional phenomena. Indium (In) atomic wires self-assembled on the Si(111) surface is a prototypical quasi-one-dimensional (quasi-1D) system undergoing a structural phase transition from the room-temperature (RT) 4×1 to the low-temperature 8×2 structure at ~120K, which is known to be a charge density wave (CDW) condensation. In this presentation, we have investigated topological solitons in Si(111)In-8×2 by combining scanning tunneling microscopy experiments and density-functional-theory calculations. Regarding solitons in Si(111)In-8×2, two different forms, one localized and the other extended in atomic scale, were recently debated [1, 2]. The short phase-shift defects (PSDs) and phase-flip defects (PFDs) on the 8×2 surface, proposed as localized solitons [1], were found to be In adatoms, i.e., extrinsic defects, but not solitons. In contrast, the long PSDs and PFDs were confirmed to be solitons without and with chirality (achiral and chiral solitons), respectively [2, 3]. Achiral solitons were found to exist in isolation and have considerable characteristic length. In contrast, isolated chiral solitons were not observed, indicating that their formation is prohibited due to their breakage of the 8×2. Chiral solitons can exist only when they are trapped by In adatoms and constitute a part of a closed-loop domain wall which separates the two 8×2 domains.
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