scholarly journals Finite-temperature effects on the superfluid Bose–Einstein condensation of confined ultracold atoms in three-dimensional optical lattices

2009 ◽  
Vol 42 (9) ◽  
pp. 095302 ◽  
Author(s):  
T P Polak ◽  
T K Kopeć
Keyword(s):  
Finite Temperature ◽  
Temperature Effects ◽  
Ultracold Atoms ◽  
Optical Lattices ◽  
Three Dimensional ◽  
Einstein Condensation ◽  
Bose Einstein Condensation ◽  
Bose Einstein

scholarly journals Bose-Einstein condensation superconductivity induced by disappearance of the nematic state

2020 ◽  
Vol 6 (45) ◽  
pp. eabb9052
Author(s):  
Takahiro Hashimoto ◽  
Yuichi Ota ◽  
Akihiro Tsuzuki ◽  
Tsubaki Nagashima ◽  
Akiko Fukushima ◽  
...  
Keyword(s):  
Ultracold Atoms ◽  
Degrees Of Freedom ◽  
Photoemission Spectroscopy ◽  
Einstein Condensation ◽  
Energy Bands ◽  
Iron Based Superconductors ◽  
Bose Einstein Condensation ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Nematic State ◽  
Bose Einstein

The crossover from the superconductivity of the Bardeen-Cooper-Schrieffer (BCS) regime to the Bose-Einstein condensation (BEC) regime holds a key to understanding the nature of pairing and condensation of fermions. It has been mainly studied in ultracold atoms, but in solid systems, fundamentally previously unknown insights may be obtained because multiple energy bands and coexisting electronic orders strongly affect spin and orbital degrees of freedom. Here, we provide evidence for the BCS-BEC crossover in iron-based superconductors FeSe1 − xSx from laser-excited angle-resolved photoemission spectroscopy. The system enters the BEC regime with x = 0.21, where the nematic state that breaks the orbital degeneracy is fully suppressed. The substitution dependence is opposite to the expectation for single-band superconductors, which calls for a new mechanism of BCS-BEC crossover in this system.

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