During the last decade, we have established a new class of one dimensional electronic systems with charge density wave (CDW) grounds states, namely, the metal atomic wire arrays grown on silicon surfaces [1, 2]. These materials provide an unprecedented platform to investigate and control various microscopic interactions of one-dimensional electrons with an atomic scale resolution. In the present talk, I will discuss the real space observation of solitons along indium atomic wires in their CDW state by scanning tunneling microscopy and spectroscopy. Although solitons in CDW states have been extensively studied since the prediction of Su, Schrieffer, and Heeger in 1980, the direct observation of a soliton was hampered by its microscopic dimension and high mobility. The unique four-fold degeneracy of the present CDW state leads to various topological defects, among which intrinsic solitons are clearly distinguished and imaged, for the first time for a commensurate CDW system. The electronic structure and the dynamics of solitons are discussed. The prospects of the microscopic soliton research in a wider context for ¡®topological matter¡¯ will be introduced.

[1] H. W. Yeom et al, Phys. Rev. Lett. 82, 4898 (1999).
[2] P. C. Snijders and H. H. Weitering, Rev. Mod. Phys. 82, 307 (2010).