Ferroelectrics are very useful materials that interact strongly with electric fields, and have revolutionized, for only one example, medical ultrasound. New ferroelectrics have led to hand-held medical scanners, like in Star Trek, and have played significant role in increasing survival rates for battlefield casualties, lower infant mortality, and safety of the oceans through SONAR. In order to improve ferroelectrics, scientists must understand them. Whereas varying temperature or chemistry lead to complex changes in properties, applying pressure should be simpler to understand, as it simply brings the atoms closer together. The original idea of how ferroelectrics work, due to Slater in the 1950s, is that the atoms rattle around, and with pressure there is less room to rattle so there should be less ferroelectricity under pressure. Experiments in the 1980s bore this out. However, in the 2000s, theory and then experiments claimed that ferroelectricity was re-entrant, and came back at ultra-high-pressures. In the 2010s, Ahart performed some very detailed measurements in the diamond anvil cell on lead titanate, a classic ferroelectric, expecting to find agreement if ferroelectricity came back under pressure. But the experiments showed otherwise, and were in agreement with the old 1980s experiments. Big computer computations, however, seemed to agree with the work in the 2000s and the unresolved situation persisted. In the highlighted work, published in Physical Review Letters, Cohen, Hemley and colleagues, show that a previously unknown crystal structure is formed at high pressures, and that other distortions occur at intermediate pressures.

For more information, see: Phys. Rev. Lett. 133, 236801 – Published 3 December, 2024 DOI: https://doi.org/10.1103/PhysRevLett.133.236801