Gate-controlled BCS-BEC crossover in a two-dimensional superconductor

Inducing a crossover In conventional superconductors, the electron pairs responsible for superconductivity are large and overlapping. Starting from this so-called Bardeen-Cooper-Schrieffer (BCS) limit, increasing interactions can set system on path of to opposite limit small, tightly bound that undergo Bose-Einstein condensation (BEC). Nakagawa et al. intercalated lithium ions into insulating material zirconium nitride chloride, varying carrier density across range (see Perspective by Randeria). This induced enabled enter regime between BCS BEC limits. Science , issue p. 190 ; see also 132