Spin-orbit effects in ferroelectric PbTiO3 under tensile strain

Abstract : We report a study based on first-principles calculations complemented by a tight-binding approach and a k⋅p model of the spin-orbit effects in epitaxially strained PbTiO3. The imposed biaxial tensile strain allows us to rotate the electrical polarization of PbTiO3 from out-of-plane to in-plane directions through structural phase transitions between a tetragonal, monoclinic, and orthorhombic phase. It is found that Ti d-state conduction bands exhibit two strong Rashba-like spin-splitting parameters of (1) 0.39 eV Å at a tensile strain η=1.55% due to a polarization rotation in the monoclinic phase and (2) 1.08 eV Å under large tensile strain of 3.8% due to band anticrossing in the orthorhombic phase. Remarkably, we also identified the presence of a quasipersistent spin texture for the band with a dyz−zx character in the orthorhombic phase. We then conclude that using strain could be an interesting way to tune the spin-orbit effects in ferroelectric materials with technological interests.