Triangular Mott-Hubbard insulator phases of Sn/Si(111) and Sn/Ge(111) surfaces.

Observation of a Mott insulating ground state for Sn/Ge(111) at low temperature.

We report an investigation on the properties of 0.33 ML of Sn on Ge(111) at temperatures down to 5 K. Low-energy electron diffraction and scanning tunneling microscopy show that the (3x3) phase formed at approximately 200 K, reverts to a new ((square root 3)x(square root 3))R30 degrees phase below 30 K. The vertical distortion characteristic of the (3x3) phase is lost across the phase transitio...

First Principles Calculations of Charge and Spin Density Waves of √ 3 - Adsorbates on Semiconductors

We present ab-initio electronic structure results on the surface of √ 3 × √ 3 adsorbates. In particular, we address the issue of metal-insulator instabilities, charge-density-waves (CDWs) or spin-density-waves (SDWs), driven by partly filled surface states and their 2D Fermi surface, and/or by the onset of magnetic instabilities. The focus is both on the newly discovered commensurate CDW transi...

Scanning Tunneling Microscopy and Photoelectron Spectroscopy Studies of Si(111) and Ge(111) Surfaces: Clean and Modified by H or Sn Atoms

Lithium intercalation behaviors in Ge and Sn crystalline surfaces.

Fast Li transport inside the Si electrode of Li-ion batteries is retarded at the electrode surface. We investigated the intercalation of a Li atom into the surface and subsurface layers of Ge and Sn using density functional calculations. In the Ge and Sn surfaces, the Li atom diffuses about four and twelve times faster, respectively, along the <100> direction than along the <111> direction. The...

Dynamical fluctuations and the √ 3 × √ 3 ↔ 3 × 3 transition in α - Sn / Ge ( 111 ) and Sn / Si ( 111 )

A critical review of our understanding of the reversible phase transition √ 3 × √3 ↔ 3 × 3 for the α-phase of the Sn/Ge(111) and Sn/Si(111) interfaces is presented. Experimental data and theoretical calculations suggest the following. (a) Sn/Ge(111) presents a reversible phase transition associated with the freezing of a surface soft phonon. At high temperature the dynamical fluctuations of the...