The Efimov effect plays a central role in few-body systems at ultracold temperature and
has thus accelerated a lot of studies on its manifestation in the collisional stability of the
quantum degenerate gases. Near broad Feshbach resonances, Efimov physics has been stud
ied both theoretically and experimentally through the zero-energy scattering observables.
We have extended the theoretical studies of Efimov physics to a much broader extent. In
particular, we have investigated the three-body Efimov physics near narrow Feshbach reso
nances and have also identified the Efimov features beyond the zero temperature limit. We
have found, near a narrow Feshbach resonance, the non-trivial contribution from both of the
resonance width and the short-range physics to the three-body recombination and vibra
tional dimer relaxation. Remarkably, the collisional stability of the Feshbach molecules are
found to be opposite to that near the broad resonances: an increased stability for molecules
made by bosons and a decreased stability for those made by fermions. The universal physics
observed near the narrow Feshbach resonances is further found not to be limited to the zero
temperature observables. We have found that the general features of Efimov physics and
those pertaining to a narrow resonance are manifested in different energy ranges above zero
temperature. This opens the opportunity to observe Efimov physics by changing the col
lisional energy while keeping the atomic interaction fixed. The landscape of the universal
Efimov physics is thus delineated in both of the interaction and the energy domain. We have
also investigated Efimov physics in heteronuclear four-body systems where the complexity
can be reduced by approximations. In particular, we have proposed ways for controllable
production of the Efimov tri-atomic molecules by three-body or four-body recombinations
involving four atoms. We have also confirmed the existence of four-body Efimov effect in
a system of three heavy particles and one light particle, which has resolved a decade-long
controversy on this topic. Finally, we have studied the collisional properties of four identical
bosons in 1D, which is important to the experiments on the quantum gases confined in the
1D optical lattices.
The Efimov effect plays a central role in few-body systems at ultracold temperature andhas thus accelerated a lot of studies on its manifestation in the collisional stability of thequantum degenerate gases. Near broad Feshbach resonances, Efimov physics has been studied both theoretically and experimentally through the zero-energy scattering observables.We have extended the theoretical studies of Efimov physics to a much broader extent. Inparticular, we have investigated the three-body Efimov physics near narrow Feshbach resonances and have also identified the Efimov features beyond the zero temperature limit. Wehave found, near a narrow Feshbach resonance, the non-trivial contribution from both of theresonance width and the short-range physics to the three-body recombination and vibrational dimer relaxation. Remarkably, the collisional stability of the Feshbach molecules arefound to be opposite to that near the broad resonances: an increased stability for moleculesmade by bosons and a decreased stability for those made by fermions. The universal physicsobserved near the narrow Feshbach resonances is further found not to be limited to the zerotemperature observables. We have found that the general features of Efimov physics andthose pertaining to a narrow resonance are manifested in different energy ranges above zerotemperature. This opens the opportunity to observe Efimov physics by changing the collisional energy while keeping the atomic interaction fixed. The landscape of the universalEfimov physics is thus delineated in both of the interaction and the energy domain. We havealso investigated Efimov physics in heteronuclear four-body systems where the complexitycan be reduced by approximations. In particular, we have proposed ways for controllableproduction of the Efimov tri-atomic molecules by three-body or four-body recombinationsinvolving four atoms. We have also confirmed the existence of four-body Efimov effect ina system of three heavy particles and one light particle, which has resolved a decade-longcontroversy on this topic. Finally, we have studied the collisional properties of four identicalbosons in 1D, which is important to the experiments on the quantum gases confined in the1D optical lattices.
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