What is BCs-BEC crossover Interpolation between fermionic superfluids to bosonic superfluids Transition from loosely bound Cooper pairs to tightly bound molecules The schematic excitation spectrum BCS intermediate BEC ◎a ●● ○oWhat is BCS-BEC Crossover ◼ Interpolation between fermionic superfluids to bosonic superfluids ◼ Transition from loosely bound Cooper pairs to tightly bound molecules. ◼ The schematic excitation spectrum: