Giant superconducting fluctuations in the compensated semimetal FeSe at the BCS-BEC crossover.

ABSTRACT: The physics of the crossover between weak-coupling Bardeen-Cooper-Schrieffer (BCS) and strong-coupling Bose-Einstein condensate (BEC) limits gives a unified framework of quantum-bound (superfluid) states of interacting fermions. This crossover has been studied in the ultracold atomic systems, but is extremely difficult to be realized for electrons in solids. Recently, the superconducting semimetal FeSe with a transition temperature T_c=8.5 K has been found to be deep inside the BCS-BEC crossover regime. Here we report experimental signatures of preformed Cooper pairing in FeSe, whose energy scale is comparable to the Fermi energies. In stark contrast to usual superconductors, large non-linear diamagnetism by far exceeding the standard Gaussian superconducting fluctuations is obse

SUBMITTER: Kasahara S 

PROVIDER: S-EPMC5056430 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature