Elastic and inelastic helium atom scattering experiments have been carried out on the ${\mathrm{KTaO}}_3\mathrm{}\left(001\right)\mathrm{}$ surface, prepared by cleaving in situ under ultra high vacuum conditions. Several unusual observations were recorded in the helium diffraction studies. These include the appearance of metastable surface features immediately after cleaving (which decay to the stable $(1\mathrm{}\times 1)$ surface after a few hours), the formation and dissolution of small $(2\mathrm{}\times 1)$ and $(1\mathrm{}\times 2)$ domains depending on the thermal history of the surface, large hysteresis in the diffraction beam intensities measured for surface temperatures between 200 K and 50 K depending on whether the surface is being warmed or cooled, and permanent changes in the diffraction intensities as a result of poling normal to the surface plane. The single-phonon energy-transfer experiments yield three surface phonon dispersion branches in the $〈100〉$ and $〈110〉$ high-symmetry azimuths. Calculations of the lattice dynamics using the VASP approach are described and the results are compared with the measurements.

• Received 22 January 2003

DOI:https://doi.org/10.1103/PhysRevB.68.045402