Model of two-dimensional electron gas formation at ferroelectric interfaces

Abstract

The formation of a two-dimensional electron gas at oxide interfaces as a consequence of polar discontinuities has generated an enormous amount of activity due to the variety of interesting effects it gives rise to. Here we study under what circumstances a similar processes can also take place underneath ferroelectric thin films. We use a simple Landau model to demonstrate that in the absence of extrinsic screening mechanisms a monodomain phase can be stabilized in ferroelectric films by means of an electronic reconstruction. Unlike in the LaAlO3/SrTiO3 heterostructure, the emergence with thickness of the free charge at the interface is discontinuous. This prediction is confirmed by performing first principles simulations of free standing slabs of PbTiO3. The model is also used to predict the response of the system to an applied electric field, demonstrating that the two-dimensional electron gas can be switched on and off discontinuously and in a non-volatile fashion. Furthermore, the reversal of the polarization can be used to switch between a two-dimensional electron gas and a two-dimensional hole gas, which should, in principle, have very different transport properties. We discuss the possible formation of polarization domains and how such configuration competes with the spontaneous accumulation of free charge at the interfaces.

Interfacial Multiferroics of TiO2/PbTiO3 Heterostructure Driven by Ferroelectric Polarization Discontinuity

“…On the other hand, similar to n-type interface, the stability of ferromagnetic ordering also depends on the polarization strength of bulk PbTiO 3 . As shown in Figure 7(a), there is no energy difference between FM and AFM ordering when the polarization strength is small and the interface is paramagnetic 13 without persistent spin-polarization. When the ferroelectric polarization increases above ~0.6 C/m 2 , the conductive state becomes spin-polarized and the FM ordering is energetically more favorable than the AFM ordering.…”

Effects of ferroelectric polarization on surface phase diagram: Evolutionary algorithm study of theBaTiO3(001) surface

“…As a prototypical ferroelectric material, barium titanate (BaTiO 3 , BTO) plays a vital role in numerous applications and has been intensively studied theoretically [9][10][11][12][13][14][15][16] As shown in Fig. 1, BTO has a perovskite structure and undergoes a structural transition from highsymmetry cubic phase to low-symmetry tetragonal phase when lowering temperature across ∼400 K [17].…”

Thermooptical evidence of carrier-stabilized ferroelectricity in ultrathin electrodeless films

“…We note that the obtained distribution ρ ( z ) is in contrast to a model assumption in ref. 44 , where the free charges were a priori placed at the film’s surfaces only and not in the film’s interior.…”