Transport properties in doped Mott insulator epitaxial La_1-yTiO_3+δ thin films

We report on the transport properties, Hall effect and resistivity, of epitaxial La1-yTiO3+δ thin films. The materials, grown by molecular beam epitaxy, display a temperature independent Hall coefficient and a characteristic T2 dependence of the resistivity over a wide temperature range, extending from a few Kelvin to 500 K. These transport properties are shown to be consistent with small polaron metallic conduction with a dominant optical phonon mode whose energy, ħω0=80 K, is characteristic of the tilt/rotation of the oxygen octahedra in perovskite materials. © 2001 The American Physical Society.