Density and spatial distribution of charge carriers in the intrinsicn-typeLaAlO3-SrTiO3interface

Abstract

In order to establish the density and spatial distribution of charge carriers intrinsic to the n-type LaAlO 3 -SrTiO 3 heterointerface, we carry out first-principles calculations on the ͑LaAlO 3 ͒ n ͑SrTiO 3 ͒ 15 slab model with n = 2 -10. As the thickness of the LaAlO 3 layer increases, the charge transfer from LaAlO 3 to SrTiO 3 converges to half an electron per two-dimensional unit cell. It is found that the electrons in the conduction band of SrTiO 3 consist of various types of interface-bound states. The mobile electrons evaluated by excluding those states tightly bound to the interface within 2 nm or having large effective masses are in good agreement with the experimental carrier densities for all LaAlO 3 thicknesses, suggesting that the loosely bound states play a major role in the transport property. A large calculation including up to ͑LaAlO 3 ͒ 5 ͑SrTiO 3 ͒ 30 shows that about 70% of electrons are confined within 3 nm from the interface, which is in good comparison with the experiments. It is found that the transferred electrons decay exponentially at short distances from the interface, but there is a crossover to an algebraically decaying region at ϳ4 nm.

Collapse of electrons to a donor cluster inSrTiO3

“…In that model, instead of constituting spherical or cylindrical dopant clusters inside STO, the electron-providing material such as LAO is outside the bulk STO and forms a planar interface with STO over which electrons spill out. The width of the electron distribution layer inside STO derived using the Thomas-Fermi approximation 19 is consistent with results got from ab initio calculations and other non-mean-field microscopic models [24][25][26][27][28][29] . Therefore, it is natural to expect that the Thomas-Fermi approach is a good approximation for different geometries (spherical and cylindrical) as well, since in this work we also deal with spatial scales larger than the lattice constant.…”

“…It is simple yet has shown reasonable agreement with more exact calculations [24][25][26][27][28][29] in the planar STO model 19 . In that model, instead of constituting spherical or cylindrical dopant clusters inside STO, the electron-providing material such as LAO is outside the bulk STO and forms a planar interface with STO over which electrons spill out.…”

Interface superconductivity

“…(Right) Spatial dependence of the square of the associated sub-band eigenfunctions in the direction perpendicular to the interface; d refers to dxy orbitals while d ⊥ refers to dxz/dyz orbitals (from Ref. [38]). The orbital character of the states is shown in both panels; for each orbital a superscript labels the energy of the band at the Gamma point.…”

Theory of spin-orbit coupling at LaAlO3/SrTiO3interfaces and SrTiO3surfaces

“…Method: Besides bulk STO, we calculate (i) LAO/STO (1.5/6.5 layers) [22,23] which is symmetric with two ntype interfaces, (ii) LAO/STO (4/4) and (1/1) which is asymmetric with n-and p-type interfaces [24], (iii) vacuum/LAO/STO (3/1/4) which has a single n-type interface [25,26], (iv) vacuum/STO (3/7.5) with a SrO terminated surface. We fix the in-plane lattice constant of the supercells to the calculated equilibrium value of STO, and optimize the internal coordinates.…”