Eur. Phys. J. D (2016) 70: 220
https://doi.org/10.1140/epjd/e2016-70250-2

Regular Article

Anomalous pseudogap in population imbalanced Fermi superfluids

¹ Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, 211 019 Allahabad, India
² Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, 400085 Mumbai, India

^a e-mail: madhuparna.k@gmail.com

Received: 6 April 2016
Received in final form: 31 July 2016
Published online: 25 October 2016

Abstract

In a Fermi superfluid increasing population imbalance leads initially to reduction of the transition temperature, then the appearance of modulated Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, and finally the suppression of pairing itself. We have carried out a detailed investigation of the spectral behavior of the imbalanced Fermi system and observe intriguing subgap features in the low polarization regime, and a re-entrant pseudogap state at large polarization. These weak imbalance and strong imbalance features both involve effects well beyond mean field theory. We establish them by using a Monte Carlo technique on large lattices, motivate the results in terms of the pairing field distribution, and compare them to spectroscopic results in the imbalanced unitary Fermi gas.