Peaks and widths of radio-frequency spectra: An analysis of the phase diagram of ultra-cold Fermi gases

Year: 2024

Authors: Pisani L., Pini M., Pieri P., Strinati GC.

Autors Affiliation: Univ Camerino, Sch Sci & Technol, Phys Div, I-62032 Camerino, Italy; Max Planck Inst Phys Komplexer Syst, Nothnitzer Str 38, D-01187 Dresden, Germany; Univ Bologna, Dipartimento Fis & Astron, Via Irnerio 46, I-40126 Bologna, Italy; Ist Nazl Fis Nucl, Sez Bologna, Viale Berti Pichat 6-2, I-40127 Bologna, Italy; Ist Nazl Ottica, CNR INO, I-50125 Sede Di Firenze, Firenze, Italy.

Abstract: We provide a comprehensive theoretical study of the radio -frequency (rf) spectra of a two-component Fermi gas with balanced populations in the normal region of the temperature-vs-coupling phase diagram. In particular, rf spectra are analyzed in terms of two characteristic peaks, which can be either distinct or overlapping. On the BEC side of the crossover, these two contributions are associated with a fermionic quasi-particle peak and a bosonic-like contribution due to pairing. On the BCS side of the crossover, the two peaks are instead associated with interactions between particles occurring, respectively, at high or low relative momenta. Through this two-peak analysis, we show how and to what extent the correlation between the widths of the rf spectra and the pair size, previously identified in the superfluid phase at low temperature, can be extended to the normal phase, as well as how the temperature-vs-coupling phase diagram of the BCS-BEC crossover can be partitioned in a number of distinct physical sectors. Several analytic results for the shape and widths of the rf spectra are also derived in appropriate temperature and coupling limits.

Journal/Review: RESULTS IN PHYSICS

Volume: 57      Pages from: 107358-1  to: 107358-17

More Information: Financial support from the Italian MIUR, Italy under Project PRIN2017 (20172H2SC4) and from the European Union-NextGenerationEU through the Italian Ministry of University and Research, Italy under PNRR-M4C2-I1.4 Project CN00000013 National Centre for HPC, Big Data and Quantum Computing is acknowledged.
KeyWords: BCS-BEC crossover; Ultracold Fermi gases; Radio-frequency spectroscopy; Pairing fluctuations
DOI: 10.1016/j.rinp.2024.107358