Antiferromagnetic self-ordering of a Fermi gas in a ring cavity. (15th April 2019)

• Record Type: Journal Article
• Authors: Colella, Elvia; Ostermann, Stefan; Niedenzu, Wolfang; Mivehvar, Farokh; Ritsch, Helmut
• Is Part Of: New journal of physics. Volume 21:Number 4(2019:Apr.)
• Publication Date: 2019-04-15
• Subjects: antiferromagnet -- fermions -- cavity -- self-ordering; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/ab151e
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: We explore the density and spin self-ordering of driven spin-1/2 collisionless fermionic atoms coupled to the electromagnetic fields of a ring resonator. The two spin states are two-photon Raman-coupled via a pair of degenerate counterpropagating cavity modes and two transverse pump fields. In this one-dimensional configuration the coupled atom-field system possesses a continuous U (1) translational symmetry and a discrete Z 2 spin inversion symmetry. At half filling for sufficiently strong pump strengths, the combined U (1) × Z 2 symmetry is spontaneously broken at the onset of a superradiant phase transition to a state with self-ordered density and spin structures. We predominately find an antiferromagnetic lattice order at the cavity wavelength. The self-ordered states exhibit unexpected positive momentum pair correlations between fermions with opposite spin. These strong cavity-mediated correlations vanish at higher pump strength.