Topological soliton molecule in quasi 1D charge density wave.

Soliton molecules, bound states of two solitons, can be important for the informatics using solitons and the quest for exotic particles in a wide range of physical systems from unconventional superconductors to nuclear matter and Higgs field, but have been observed only in temporal dimension for classical wave optical systems. Here, we identify a topological soliton molecule formed spatially in an electronic system, a quasi 1D charge density wave of indium atomic wires. This system is composed of two coupled Peierls chains, which are endowed with a Z topology and three distinct, right-chiral, left-chiral, and non-chiral, solitons.

Creation and annihilation of mobile fractional solitons in atomic chains.

Localized modes in one-dimensional (1D) topological systems, such as Majonara modes in topological superconductors, are promising candidates for robust information processing. While theory predicts mobile integer and fractional topological solitons in 1D topological insulators, experiments so far have unveiled immobile, integer solitons only. Here we observe fractionalized phase defects moving along trimer silicon atomic chains formed along step edges of a vicinal silicon surface.

Pseudogap and Weak Multifractality in 2D Disordered Mott Charge-Density-Wave Insulator.

We investigate electronic states of Se-substituted 1-TaS by scanning tunneling microscopy/spectroscopy (STM/STS), where superconductivity emerges from the unique Mott-charge-density-wave (Mott-CDW) state. Spatially resolved STS measurements reveal that a pseudogap replaces the Mott gap with the CDW gaps intact. The pseudogap has little correlation with the unit-cell-to-unit-cell variation in the local Se concentration but appears globally.

Dynamical Metal to Charge-Density-Wave Junctions in an Atomic Wire Array.

We investigated the atomic scale electronic phase separation emerging from a quasi-1D charge-density-wave (CDW) state of the In atomic wire array on a Si(111) surface. Spatial variations of the CDW gap and amplitude are quantified for various interfaces of metallic and insulating CDW domains by scanning tunneling microscopy and spectroscopy (STS). The strong anisotropy in the metal-insulator junctions is revealed with an order of magnitude difference in the interwire and intrawire junction lengths of 0.

Atomic structures of self-assembled epitaxially grown GdSi nanowires on Si(001) by STM.

Self-assembled rare-earth (RE) silicide nanowires (NWs) on semiconductor surfaces are considered as good candidates for creating and investigating one-dimensional electron systems because of their exceptionally anisotropic growth behavior and metallic property. While detailed atomic structures are essential to understand electronic properties of these NWs, there have been only few successful observations of atomic structures with microscopy and reliable structure models are lacking. Here, we reinvestigate gadolinium silicide NWs with high resolution scanning tunneling microscopy (STM).