Excitations in the BCS–BEC crossover regime of a superfluid Fermi gas with a Feshbach resonance

✍ Scribed by Yoji Ohashi

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 243 KB
• Volume: 437-438
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2006.03.006

✦ Synopsis

We investigate single-particle excitations at T = 0 in the BCS-BEC crossover regime of a superfluid Fermi gas. We solve the Bogoliubov-de Gennes equations in a trap, including a tunable pairing interaction associated with a Feshbach resonance. We show that the single-particle energy gap E g is dominated by the lowest-energy Andreev bound state localized at the surface of the gas, which is much smaller than the superfluid order parameter Dðr ¼ 0Þ at the center of the trap. We also calculate the rf-tunneling current spectrum I F (x). In a broad Feshbach resonance, the peak energy in I F (x) is shown to give, not E g , but Dðr ¼ 0Þ. In a narrow resonance, significant spectral weight coming from the low-energy Andreev states hides the appearance of the peak in I F (x) at x ' Dðr ¼ 0Þ. Our results for a broad resonance is in good agreement with the recent rf-tunneling measurement in a superfluid 6 Li.