title: Observation of disorder-induced 2D mott-hubbard states of the alkali-earth metal (Mg,Ba)-adsorbed Si(111) surface
abstract: We report evidence of a disorder-driven Mott-Hubbard-type localization on the alkali-earth metal (AEM) (Mg,Ba)-adsorbed Si(111)-(7x7) surface. The clean metallic Si(111) surface is found to undergo a two-dimensional (2D) metal-insulator transition as randomly distributed AEM adsorbates cause disorder on the surface. A well-defined electron-energy-loss peak unique to the insulating phase is attributed to an interband excitation between the split Hubbard bands originated from a metallic surface band at Fermi energy. A quantitative analysis of the loss peak reveals that the AEM-induced insulating surfaces are of a Mott-Hubbard type driven essentially by disorder.
authors.affiliation: Physics Department and Basic Science Research Institute, Pohang University of Science and Technology, San 31 Hyoja Dong, Pohang 790-784, Korea.
authors.initials: JR
authors.lastname: Ahn
authors.initials: SS
authors.lastname: Lee
authors.initials: ND
authors.lastname: Kim
authors.initials: JH
authors.lastname: Min
authors.initials: CG
authors.lastname: Hwang
authors.initials: JW
authors.lastname: Chung