2012/08/08 by A. Rastogi, Ankur Rastogi, J. J. Pulikkotil +3 · 52 citations
Engineering · Materials Science · Physics and Astronomy · #Atomic physics #Condensed matter physics #Electron #Electronic and Structural Properties of Oxides #Fermi gas #Fermi level #Heterojunction #Magnetic and transport properties of perovskites and related materials #Materials science #Molecular physics #Optoelectronics #Photocurrent #Physics #Quantum mechanics #Semiconductor materials and devices #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.86.075127
published in Physical Review B 86(7) (American Physical Society) · 10 pages, 8 figures
arxiv created 2012/08/08 · openalex publication_date 2012/08/16 · arxiv updated 2012/08/21 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The two-carrier transport model as proposed for the two-dimensional electron gas formed at the interfaces of oxide heterostructures is investigated by means of a combined perturbation by near-ultraviolet radiation and an electrostatic field, applied both separately and simultaneously. Comparison of the photoresponse of prototype systems such as the band insulator LaAlO3 and Mott insulator LaTiO3 films on TiO2-terminated SrTiO3 shows remarkably similarities. Two types of nonequilibrium carrier are generated in each system, each having the signature of a particular type of perturbation characterized by distinctly different relaxation processes. While the photoconducting state diminishes in a stretched exponential manner, with a temperature-dependent activation energy varying from a few tens of meV to \ensuremath≈1 to 2 meV on lowering the temperature and a relaxation time of several hours, the recovery from electrostatic gating occurs on the millisecond time scale. An attempt is also made to explain the experimental observations using ab initio density functional calculations. The calculations show that the electronic transitions associated with near-ultraviolet radiation emerge from bands located at \ensuremath≃2 eV above and below the Fermi energy, which are the Ti 3d states of the SrTiO3 substrate and of the AlO2 (TiO2) layers of the LaAlO3 (LaTiO3) films, respectively. The slow decay of the photocurrent to the unperturbed state is explained in terms of the closely spaced Ti 3dxy states in the lower conduction band, which are manifested as flatbands (or localized states) in the band structure. Such localization leads to increased carrier lifetimes, through the energy-time relationship of the uncertainty principle.