Spin-polarized two-dimensional electron gas at GdTiO3/SrTiO3 interfaces: Insight from first-principles calculations

Abstract

Two-dimensional electron gases (2DEGs) at oxide interfaces have been a topic of intensive research due to their high carrier mobility and strong confinement. Additionally, strong correlations in the oxide materials can give rise to new and interesting physics, such as magnetism and metal-insulator transitions at the interface. Using first-principles calculations based on density functional theory, we demonstrate the presence of a highly spin-polarized 2DEG at the interface between the Mott insulator GdTiO 3 and a band insulator SrTiO 3. The strong correlations in the dopant cause ferromagnetic alignment of the interface Ti atoms and result in a fully spin-polarized 2DEG. The 2DEG consists of two types of carriers distinguished by their orbital character. The majority of the interface charge is strongly localized on the Ti-d xy orbitals at the interface and a smaller fraction resides on the delocalized Ti-d xz,yz states.

Designing Nonpolar Metallic Interfaces using Insulating Transition Metal Olivine Phosphates

“…In a recent study, Betancourt et al. have observed bands of width 0.6–0.7 eV cross the E F to form a metallic interface between the perovskites GdTiO 3 and SrTiO 3 …”

Hybrid spintronic materials: Growth, structure and properties

“…To end this sub-section, we would like to briefly highlight an emerging area particularly focusing on 2D oxide interfaces. Example of which include LaAlO3/STO [302,303], LaAlO3/EuO [304,305], and others [306][307][308][309]. Due to their multitude of properties, such as superconductivity, magnetism, high charge mobility, quantum confinement, etc., these interfaces are believed to be an interesting platform for gate-controlled spin transport in a lateral geometry [310][311][312] The term ÔHeusler phaseÕ was named after Friedrich Heusler, who discovered a mysterious FM behavior in a ternary alloy formed from non-FM constituents as early as 1903 [188].…”

KTaO3—The New Kid on the Spintronics Block

“…[ 53 ] Such exciting observations encouraged the study of oxide‐oxide interfaces in other STO‐based heterostructures, such as with LaVO 3 (LVO), LaTiO 3 (LTO), CaZrO 3 , GdTiO 3 (GTO), and CaHfO 3 . [ 54–58 ] However, as the SOC in STO (measured in terms of the spin‐band splitting at the gamma point between the J = 1/2 and J = 3/2 manifolds of the t 2g states due to SOC) is not too high (17 meV), [ 44 ] a need was soon felt for an alternative material with similar mobility and other properties as STO, but with larger SOC. At least for the time being, this search appears to have culminated successfully with KTO, possibly the next wonder material.…”

“…[ 39 ] This was soon followed by the observation of 2DEGs at the interfaces of STO with other perovskite oxides such as LVO, LTO and GTO. [ 54,55,57 ] Further, the STO surface itself could be made superconducting by applying liquid gating in an electric double‐layered transistor (EDLT) configuration. [ 40 ] Finally, QHE too was observed in δ‐doped STO.…”