Temperature-Dependent Band Structure of SrTiO${}_3$ Interfaces

Abstract

We build a theoretical model for the electronic properties of the two-dimensional (2D) electron gas that forms at the interface between insulating SrTiO${}_3$ and a number of polar cap layers, including LaTiO${}_3$, LaAlO${}_3$, and GdTiO${}_3$. The model treats conduction electrons within a tight-binding approximation, and the dielectric polarization via a Landau-Devonshire free energy that incorporates strontium titanate's strongly nonlinear, nonlocal, and temperature-dependent dielectric response. The self-consistent band structure comprises a mix of quantum 2D states that are tightly bound to the interface, and quasi-three-dimensional (3D) states that extend hundreds of unit cells into the SrTiO${}_3$ substrate. We find that there is a substantial shift of electrons away from the interface into the 3D tails as temperature is lowered from 300 K to 10 K. This shift is least important at high electron densities ($\sim 10^{14}$ cm${}^{-2}$), but becomes substantial at low densities; for example, the total electron density within 4~nm of the interface changes by a factor of two for 2D electron densities $\sim 10^{13}$ cm${}^{-2}$. We speculate that the quasi-3D tails form the low-density high-mobility component of the interfacial electron gas that is widely inferred from magnetoresistance measurements.

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Cited by in corpus (7)

• Influence of the ferroelectric quantum critical point on SrTiO${}_3$ interfaces
• Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces
• Possible Flexoelectric Origin of the Lifshitz Transition in LaAlO${}_3$/SrTiO${}_3$ Interfaces
• Observation of zero-field transverse resistance in AlO${}_x$/SrTiO${}_3$ interface devices
• Evolution of domain structure with electron doping in ferroelectric thin films
• Modified transverse Ising model for the dielectric properties of SrTiO${}_3$ films and interfaces
• Influence of a Realistic Multiorbital Band Structure on Conducting Domain Walls in Perovskite Ferroelectrics