Superconductor-insulator transition in an anisotropic two-dimensional electron gas assisted by one-dimensional Friedel oscillations: (Tl,Au)/Si(100)−c(2×2)

Abstract

The recently found $(\mathrm{Tl},\mathrm{Au})/\mathrm{Si}(100)c(2\ifmmode\times\else\texttimes\fi{}2)$ two-dimensional compound which possesses spin-split surface states with peculiar spin texture and strong band anisotropy was examined using low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy observations and in situ four-probe transport measurements. Two types of the one-dimensional incommensurate Friedel oscillations were found to develop near the surface defects with the wavelengths corresponding to the nesting vectors of the $(\mathrm{Tl},\mathrm{Au})/\mathrm{Si}(100)c(2\ifmmode\times\else\texttimes\fi{}2)$ Fermi surface. In transport measurements, samples show strong localization behavior when density of defects is sufficiently high. With low density of defects, the system demonstrates a metallic behavior with fingerprints of superconducting transition at estimated ${T}_{c}=1.33\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Thus, the $(\mathrm{Tl},\mathrm{Au})/\mathrm{Si}(100)c(2\ifmmode\times\else\texttimes\fi{}2)$ system hosts a combination of fascinating properties and effects, including one-dimensional Friedel oscillations, superconductivity, and a spin-split anisotropic Fermi surface, that opens an avenue for prospective investigations of the interplay of collective electronic phenomena in atomic layer material.