Electron gas induced in SrTiO3

Abstract

This mini-review is dedicated to the 85th birthday of Prof. L. V. Keldysh, from whom we have learned so much. In this paper we study the potential and electron density depth profiles in surface accumulation layers in crystals with a large and nonlinear dielectric response such as SrTiO3 (STO) in the cases of planar, spherical and cylindrical geometries. The electron gas can be created by applying an induction D0 to the STO surface. We describe the lattice dielectric response of STO using the Landau-Ginzburg free energy expansion and employ the Thomas-Fermi (TF) approximation for the electron gas. For the planar geometry we arrive at the electron density profile n(. We extend our results to overlapping electron gases in GTO/STO/GTO heterojunctions and electron gases created by spill-out from NSTO (heavily n-type doped STO) layers into STO. Generalization of our approach to a spherical donor cluster creating a big TF atom with electrons in STO brings us to the problem of supercharged nuclei. It is known that for an atom with nuclear charge Ze, where Z > 170, electrons collapse onto the nucleus resulting in a net charge Zn < Z. Here, instead of relativistic physics, the collapse is caused by the nonlinear dielectric response. Electrons collapse into the charged spherical donor cluster with radius R when its total charge number Z exceeds the critical value Zc R/a, where a is the lattice constant. The net charge eZn grows with Z until Z exceeds Z * (R/a) 9/7 . After this point, the charge number of the compact core Zn remains Z * , with the rest Z * electrons forming a sparse Thomas-Fermi atom with it. We extend our studies of collapse to the case of long cylindrical clusters as well.

Universality of electron mobility in LaAlO3/SrTiO3 and bulk SrTiO3

“…Due to the relatively large width of this electron layer, we essentially deal with a three-dimensional system. 35,36 Such an electronic system can be described by the recent theory [37][38][39] of accumulation layers in STO based on a combination of the Landau-Ginzburg description of the dielectric response of the STO lattice and the Thomas-Fermi approximation for the degenerate electron gas. Using this theory, we show below that the three-dimensional electron density of the electronic system near the LAO/STO interface, n 3D , depends on the measured two-dimensional sheet electron density, n s , in the following way:…”

Epitaxial SrTiO 3 films with dielectric constants exceeding 25,000

“…To understand the origin of low capacitances at the buried interfaces, we calculate the carrier and potential profiles at the n -STO/undoped STO interface based on the model proposed in ref. 33 . As shown in SI Appendix , Fig.…”

Electronic Structure of FeSe Monolayer Superconductors: Shallow Bands and Correlations

“…There is a common belief that it is associated with the formation of oxygen vacancies in the SrTiO 3 substrate (in the topmost layer of TiO 2 ), occurring during the various technological steps used during film preparation, such as annealing, etching, etc. It should be noted that the formation of the electron gas at the interface with the SrTiO 3 is rather widely known phenomenon, which was studied for a long time [60]. At the same time, for FeSe/STO system this issue was not analyzed in detail and remains unexplained (see, however, recent Refs.…”