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 electronics³. 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 PbTiO₃/SrTiO₃ 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 PbTiO₃ is brought close to the so-called 'incipient ferroelectric' state.