Abstract
The crossover from Bardeen-Cooper-Schrieffer (BCS) superconductivity to Bose-Einstein condensation (BEC) is difficult to realize in quantum materials because, unlike in ultracold atoms, one cannot tune the pairing interaction. We realize the BCS-BEC crossover in a nearly compensated semimetal, Fe1+ySexTe1−x, by tuning the Fermi energy eF via chemical doping, which permits us to systematically change D/eF from 0.16 to 0.50, where D is the superconducting (SC) gap. We use angle-resolved photoemission spectroscopy to measure the Fermi energy, the SC gap, and characteristic changes in the SC state electronic dispersion as the system evolves from a BCS to a BEC regime. Our results raise important questions about the crossover in multiband superconductors, which go beyond those addressed in the context of cold atoms.
Original language | English |
---|---|
Article number | e1602372 |
Journal | Science Advances |
Volume | 3 |
Issue number | 4 |
DOIs | |
State | Published - Apr 2017 |
All Science Journal Classification (ASJC) codes
- General