Giant voltage amplification from electrostatically induced incipient ferroelectric states.

Ferroelectrics subject to suitable electric boundary conditions present a steady negative capacitance response 1,2 . When the ferroelectric is in a heterostructure, this behaviour yields a voltage amplification in the other elements, which experience a potential difference larger than the one applied, holding promise for low-power electronics 3 . So far research has focused on verifying this effect and little is known about how to optimize it. Here, we describe an electrostatic theory of ferroelectric/dielectric superlattices, convenient model systems 4,5 , and show the relationship between the negative permittivity of the ferroelectric layers and the voltage amplification in the dielectric ones. Then, we run simulations of PbTiO 3 /SrTiO 3 superlattices to reveal the factors most strongly affecting the amplification. In particular, we find that giant effects (up to tenfold increases) can be obtained when PbTiO 3 is brought close to the so-called 'incipient ferroelectric' state.