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

• DOI: 10.1126/science.abb9860
• Publication Date: 2021-03-18T19:10:35Z
• Authors: Yuji Nakagawa; Yuichi Kasahara; Takuya Nomoto; Ryotaro Arita; Tsutomu Nojima; Yoshihiro Iwasa
• Keywords: 0301 basic medicine; Superconductivity (cond-mat.supr-con); 03 medical and health sciences; Condensed Matter - Superconductivity; 0103 physical sciences; FOS: Physical sciences; 01 natural sciences

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 the system on a path of crossover to the opposite limit of small, tightly bound electron pairs that undergo Bose-Einstein condensation (BEC). Nakagawa et al. intercalated lithium ions into the insulating material zirconium nitride chloride, varying the carrier density across a large range (see the Perspective by Randeria). This induced superconductivity and enabled the system to enter the crossover regime between the BCS and BEC limits.

Science , this issue p. 190 ; see also p. 132