Au(110) (1 × 2)-to-(1 × 1) Phase Transition: A Physical Realization of the Two-Dimensional Ising Model

Abstract

We report the first measurements of the critical exponents of a phase transition at the surface of a clean metal, the Au(110) (1 \ifmmode\times\else\texttimes\fi{} 2) \ensuremath{\leftrightarrow} (1 \ifmmode\times\else\texttimes\fi{} 1) transition. The exponents $\ensuremath{\beta}$, $\ensuremath{\gamma}$, and $\ensuremath{\nu}$ and the amplitudes were measured by LEED and place the phase transition in the two-dimensional Ising universality class. The critical scattering is observed to peak above ${T}_{c}$, signaling the breakdown of the Ornstein-Zernike theory, and is in numerical accord with predictions of Fisher and Burford.