Appearance of a Domain Structure and its Electronic states in Iron Doped 1$T$-TaS$_2$ Observed using Scanning Tunneling Microscopy and Spectroscopy

In this paper, we report on scanning tunneling microscopy and spectroscopy (STM/STS) measurements on iron doped 1$T$-Ta$_{1-x}$Fe$_x$S$_2$. A novel domain structure composed of the domains with localized nature divided by the walls is observed in Ta$_{0.99}$Fe$_{0.01}$S$_2$, where the Mott transition is completely suppressed. This indicates that the melting of the Mott state accompanies the appearance of the domain structure. Since the number of walls increase in superconducting Ta$_{0.98}$Fe$_{0.02}$S$_2$, the domain walls seem to be responsible for superconductivity in iron doped 1$T$-TaS$_2$.