A first-principles study on the intrinsic asymmetric ferroelectricity of the SrTiO₃–BaTiO₃–CaTiO₃tricolor superlattice at the nanoscale

Abstract

We report a systematic theoretical study on the ferroelectric behavior of ultrathin three-component ferroelectric films, e.g., CaTiO3-BaTiO3-SrTiO3, sandwiched between electrodes. Using first-principles calculations we demonstrate that such structures have intrinsic asymmetric ferroelectricity which is robust even at the nanoscale. In addition, there exists a certain relationship between the polarization directions and geometric stacking sequences of the superlattices. Specifically, the lowest energy states always have polarizations pointing from CaTiO3 via BaTiO3 to SrTiO3, while the sequence in the metastable states is SrTiO3-BaTiO3-CaTiO3. Therefore we were able to distinguish one ferroelectric state from its opposite state by means of their geometric stackings along the polarization directions. Besides this, band alignment analysis reveals that such structures are well behaved at the metal/ferroelectric interface, confirming the credibility and reliability of our first-principles calculation. Our finding may suggest a controllable and unambiguous way to build ferroelectric and multiferroic tunnel junctions.

Electronic structure, optical and dielectric properties of BaTiO3/CaTiO3/SrTiO3 ferroelectric superlattices from first-principles calculations

“…It is also clear that the smallest direct band gap is 2.39eV at the Г point. Our results are in consistency with Please do not adjust margins Please do not adjust margins the band gap of 2.3 eV according to Gao et al, 32 but they didn't show the band structure. Considering that there is no detailed report about the experimental band gap, we compared with the gaps of BaTiO 3 , CaTiO 3 , and SrTiO 3 .…”

Role of Lone‐Pairs in Driving Ferroelectricity of Perovskite Oxides: An Orbital Selective External Potential Study

“…[29] Generally, a ferroelectric state corresponds to a double-well potential profile, whereas a single-well profile indicates the system is in paraelectric state. The λ-method was used, which describes the potential profile of the soft mode distortions with parameter λ, where λ = +1 and −1 correspond to the polarization "up" and "down" states, respectively.…”

“…The influence of the applied potential on the ferroelectricity of BTO was then investigated. The λ ‐method was used, which describes the potential profile of the soft mode distortions with parameter λ , where λ = +1 and −1 correspond to the polarization “up” and “down” states, respectively . Generally, a ferroelectric state corresponds to a double‐well potential profile, whereas a single‐well profile indicates the system is in paraelectric state.…”

Theoretical studies of all-electric spintronics utilizing multiferroic and magnetoelectric materials

“…Gao et al's theoretical work [36] demonstrated that the ultrathin three-component ferroelectric films have intrinsic asymmetric ferroelectricity which is robust even at the nanoscale. More interestingly, the asymmetric ferroelectricity would be more obvious when the tricolor superlattice was contacted with ferromagnetic electrode materials such as SrRuO 3 (Fig.…”