Two-dimensional electron gases (2DEGs) can form at the surface of oxides and semiconductors or in carefully designed quantum wells and interfaces. Depending on the shape of the confining potential, 2DEGs may experience a finite electric field, which gives rise to relativistic effects such as the Rashba spin-orbit coupling. Although the amplitude of this electric field can be modulated by an external gate voltage, which in turn tunes the 2DEG carrier density, sheet resistance and other related properties, this modulation is volatile. Here, we report the design of a ''ferroelectric'' 2DEG whose transport properties can be electrostatically switched in a non-volatile way. We generate a 2DEG by depositing a thin Al layer onto a SrTiO3 single crystal in which 1 percent of Sr is substituted by Ca to make it ferroelectric. Signatures of the ferroelectric phase transition at 25 K are visible in the Raman response and in the temperature dependences of the carrier density and sheet resistance that shows a hysteretic dependence on electric field as a consequence of ferroelectricity. We suggest that this behavior may be extended to other oxide 2DEGs, leading to novel types of ferromagnet-free spintronic architectures.
@article{arxiv.2007.03344,
title = {A switchable two-dimensional electron gas based on ferroelectric Ca:SrTiO$_3$},
author = {Julien Bréhin and Felix Trier and Luis M. Vicente-Arche and Pierre Hemme and Paul Noël and Maxen Cosset-Chéneau and Jean-Philippe Attané and Laurent Vila and Anke Sander and Yann Gallais and Alain Sacuto and Brahim Dkhil and Vincent Garcia and Stéphane Fusil and Agnès Barthélémy and Maximilien Cazayous and Manuel Bibes},
journal= {arXiv preprint arXiv:2007.03344},
year = {2020}
}