Model of two-dimensional electron gas formation at ferroelectric interfaces
Bristowe, N. C.
Littlewood, P. B.
- Publisher: American Physical Society
11000/11 | Condensed Matter - Mesoscale and Nanoscale Physics | QD473 | Condensed Matter - Materials Science | 11000/12 | 11000/13
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 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 nonvolatile 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.
We acknowledge computing resources of CAMGRID in Cambridge, DIPC in San Sebastian, and the Spanish Super- ´ computer Network (RES). This work has been partly funded by MINECO-Spain (Grant No. FIS2012-37549-C05), UK’s EPSRC, and the ARC project TheMoTherm (Grant No. 10/15- 03). Work at Argonne was supported by DOE-DES under Contract No. DE-AC02-06CH11357. Ph.G. acknowledges a Research Professorship of the Francqui Foundation (Belgium), and N.C.B. a research fellowship from the Royal Commission for the Exhibition of 1851 and support from the Thomas Young Centre under grant TYC-101.