Fermi-degenerate quantum atomic gases

A Fermi-degenerate dilute gas is a fountain of quantmn phenomena characteristic exactly of Fermi gases. Specifically, there can be observed the phenomenon known as Pauli blocking. Pauli blocking is a consequence of the fact that identical fermions cannot occupy the same quantum state. Under quantmn-degenerate conditions, all the lower quantum states are occupied. This limits the possibility for the interacting 

A Fermi-degenerate gas can coexist with a Bose-Einstein condensate. This was observed, for example, in experiments with an ultracold atomic mixture of Li atoms (bosons) and Li atoms (fermions) at a temperature of T = 0.28/l(K and Tf=0.2Tc, where Tp and Tc are the Fermi and the Bose-Einstein condensation critical temperature, respectively (Schreck et al. 2001). 

The possibility of pairing fermionic atoms (Cooper pairing) to form bosonic atoms has far-reaching consequences, as far as studies into such phenomena as superfluidity and superconductivity under the controlled conditions of quantum degenerate gases are concerned (see Section 8.5). 

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The length R is an intrinsic parameter of a Eeshbach resonance. It characterizes the width of the resonance. From Equations 10.1 and 10.2 we see that small W and, consequently, large R correspond to narrow resonances, whereas large W and small R lead to wide resonances. The term wide is generally used when the length R drops out of the problem, which, according to Equation 10.3, requires the condition kR 1. In a quantum degenerate atomic Fermi gas the characteristic momentum... 

Fig. 8.2 A quantum degenerate gas of ultracold atoms reaches degeneracy when the matter waves of neighboring atoms overlap (a) at absolute zero, gaseous bosonic atoms all end up in the lowest energy state (b) fermions, in contrast, fill the states with one atom per state, and the energy of the highest filled state at T = 0 is the Fermi energy Ep ...

The first step was the production of ultracold molecules from a quantum-degenerate Fermi gas of atoms at a temperature below 150 nK (Regal et al. 2003). The low binding energy of the molecules was controlled by detuning the magnetic field away from the Feshbach resonance. Clear evidence of diatomic molecules was achieved through direct, radio-frequency spectroscopic detection of molecules. 

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