In recent years, several experimental works have shown that “negative capacitance” can be attained in a ferroelectric thin film placed in series with a paraelectric [1]. To explain this, they claim that the negative capacitance is realized by suppression of spontaneous polarization in the ferroelectric due to the depolarizing effect coming from the paralectric film. However, such explanation has been criticized due to the fact that any such depolarizing effects are usually cancelled in ferroelectric materials through the formation of polarization domains.

In this talk, I will try to present a more convincing explanation of the mechanism for negative capacitance based on first-principles simulation results of a multidomain ferroelectric-paraelectric bilayer capacitor under bias voltage [2]. The finite-voltage simulations are performed using the orbital-separation approach [3] within the Kohn-Sham formalism of density functional theory. We show that domains evolve in an antiferroelectric-like way, and that negative capacitance can emerge as a result of monodomain formation under bias.

Reference:
[1] G. Catalan, D. Jiménez, A. Gruverman, Nature Mater. 14, 137 (2015).
[2] S. Kasamatsu, S. Watanabe, C. S. Hwang, and S. Han, Adv. Mater. 28, 335 (2016).
[3] S. Kasamatsu, S. Watanabe, and S. Han, Phys. Rev. B 84, 085120 (2011); Phys. Rev. B 92, 115124 (2015).