Ferroelectricity is believed to be induced, since it’s discovery in 1920, that a bulky region (10~100nm) so called “domain” is required to stabilize and switch it. Here, we break the 100-years myth by introducing flat phonon bands into the history of ferroelectricity [1]. As dispersionless (flat) energy band at momentum space has been known to induce localized states at real space and to cause unusual phenomena such as graphene superconductivity, we, for the first time, show that flat phonon bands in a ferroelectric HfO₂ induce localized dipoles within a few-angstroms scale. We propose to switch these irreducibly small dipoles in our daily semiconductors and pave a way to materialize ultimate-density memories whose densities will reach up to ~100 TB, which will open the era of “Atomic Semiconductor”.

[1] H. -J. Lee et al., Science 369, 1343 (2020)