Anomalous change of electronic properties for uniaxial-strained LaAlO₃/SrTiO₃ (001) heterostructure

The first-principles electronic structure calculation was applied to investigate the electronic properties of the LaAlO3/SrTiO3 (001) heterostructure system (HSs) under strain. The results show that the distorted structure at the interface determines the occupied orbitals of 2DEG, further resulting in different sensitivities of interfacial charge carrier density, electron effective mass, electron mobility, and electrical conductivity on strain. The interfacial metallic states of tensile-strained and biaxial-compressive-strained LaAlO3/SrTiO3 (001) HSs mainly occupy Ti 3dxy orbitals, which is the same for unstrained HSs. Then, the electron effective mass slightly decreases with tensile strain, which leads to a higher electrical conductivity. Different from biaxial-compressive-strained LaAlO3/SrTiO3 (001) HSs with Ti 3d(xy) occupied orbitals, the Ti 3d(yz) orbitals are occupied for uniaxial-compressive-strained HSs, thus leading to a remarkably increased electron effective mass and sharply decreased electrical conductivity. These results give us a guidance to effectively modify the interfacial electronic characteristics of LaAlO3/SrTiO3 (001) HSs by strain.