Ultracold atoms have become one of the most exciting platforms to synthesize novel condensed matter physics. Here we realize a sawtooth superradiance lattice in Bose-Einstein condensates and investigate its chiral edge currents. Based on one-dimensional superradiance lattice (SL) in standing wave-coupled electromagnetically induced transparency, a far-detuned standing-wave field is introduced to synthesize a magnetic field. The relative spatial phase between the two standing-wave coupling fields introduce a magnetic flux in the sawtooth loop transitions of the lattice. This flux determines the moving direction of excitations created in the SL and results in nonsymmetric reflectivities when the SL is probed in two opposite directions. Our work demonstrates an in situ technique to synthesize and detect artificial gauge field in cold atoms.

We report on the production of Bose–Einstein condensates of sodium atoms in the hyperfine state | F = 2 , m F = 2 ⟩ in a crossed optical dipole trap using D 2 gray molasses. We use the gray molasses sub-Doppler cooling technique to obtain an atomic sample of 3 × 10 8 at 56 µK. After the radio frequency (RF) evaporation cooling in an optically plugged magnetic trap, we transfer the atoms sample of 2.5 × 10 6 at 5.7 µK to a crossed optical dipole trap where a pure condensate with an atom number of 2 × 10 5 and lifetime of 6.3 s is obtained by further evaporation. We compare the cooling process of sodium atoms in the | 2 , 2 ⟩ and the | 1 , 1 ⟩ states by evaporation in the optical trap, and also observe the different three-body loss rates by the lifetime measurement.

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We study the electromagnetically induced-absorption-like (EIA-like) effect for an n-type system in an 87 Rb Bose-Einstein condensate (BEC) using the absorption imaging technique for coupling and driving lasers operating at the 𝐷1 and 𝐷2 lines of 87 Rb. The coherent effect is probed by measuring the number of atoms remaining after the BEC is exposed to strong driving fields and a weak probe field. The absorption imaging technique accurately reveals the EIA-like effect of the n-type system. This coherent effect in an n-type system is useful for optical storage, tunable optical switching, and so on.