Using LEED to study specific heat anomalies of adsorbed overlayers

Abstract

Near a second order phase boundary the leading thermal dependence of the integrated intensities of “extra” LEED beams is proportional to ∓| T− T c| 1-α for T ≷ T c, where α is the specific heat critical exponent. This behavior occurs when the correlation length exceeds the characteristic length of the instrument but is less than the characteristic size of defect-free regions. We illustrate these ideas using the structure factor of a p(2×2) overlayer on a triangular lattice, simulated using Monte Carlo. Similar behavior can appear in other probes of phenomena dependent solely on finite-range correlations.