Ferroelectric ice

摘要

Water molecules are dipolar, and while tumbling in the liquid state can be partly aligned by an electric field (Fig. 1). In ice, however, although the molecules are essentially static, there is no overall alignment (Fig. 2). A question that has long fascinated researchers is whether there is a form of normal ice in which the molecular dipoles have a net orientation towards one direction. Recent papers have revived an old debate about whether such 'ferroelectric' ice exists, and if so, what implications its existence would have for our understanding of condensed matter. The groups concerned report definite experimental evidence that at least partial ferroelectric alignment can be induced in normal ice, either by interaction with a substrate, or by doping with impurities.