Production of dual species Bose–Einstein condensates of ^(39)K and ^(87)Rb

We report the production of^(39) K and^(87) Rb Bose–Einstein condensates(BECs) in the lowest hyperfine states |F =1, m_(F) = 1 simultaneously. We collect atoms in bright/dark magneto-optical traps(MOTs) of^(39) K/^(87) Rb to overcome the light-assisted losses of^(39) K atoms. Gray molasses cooling on the D1 line of the^(39) K is used to effectively increase the phase density, which improves the loading efficiency of^(39) K into the quadrupole magnetic trap. Simultaneously, the normal molasses is employed for^(87) Rb. After the microwave evaporation cooling on^(87) Rb in the optically plugged magnetic trap,the atoms mixture is transferred to a crossed optical dipole trap, where the collisional properties of the two species in different combinations of the hyperfine states are studied. The dual species BECs of^(39) K and^(87) Rb are obtained by further evaporative cooling in an optical dipole trap at a magnetic field of 372.6 G with the background repulsive interspecies scattering length a_(KRb)= 34 a_(0)(a_(0) is the Bohr radius) and the intraspecies scattering length a_K= 20.05 a_(0).

Achieving ultracold Bose–Fermi mixture of^(87)Rb and^(40)K with dual dark magnetic-optical-trap

We demonstrate that dual dark magnetic-optical-traps(MOTs)have great importance in the two-species^(87)Rb and^(40)K mixture compared with dual bright MOTs.The dark MOT has a little improvement in the trapping of single-species^(87)Rb or^(40)K gases compared with bright MOT.For the case of loading two-species^(87)Rb and^(40)K simultaneously,the improvement of^(40)K in the dual dark MOTs is mainly from the reduction of light-assisted collision losses.The dual dark MOTs employ a pair of conical lenses to produce the hollow beam for repump laser with high efficiency.The number and density of^(87)Rb and^(40)K atoms after evaporative cooling in the hybrid magnetic trap with dark MOT loading are compared with those in bright MOT.The atoms with large number and high density make it easier to realize the quantum degenerate of Bose-Fermi mixture.

Preparation of a two-state mixture of ultracold fermionic atoms with balanced population subject to the unstable magnetic field

We report a novel method to prepare a mixture of ^(40)K Fermi gas having an equal population of the two ground magnetic spin states confined in an optical dipole trap,in the presence of an noisy quantization(magnetic)field.We realize the equal population mixture by applying a series of RF pulses.We observe the dependence of the population distribution between two spin states on the number of the applied RF pulses and find that the decoherence effects leading to the population fluctuations are overcome by the high number of RF pules.Our demonstrated technique can be potentially used in the precision measurement experiments with ultracold gases in noisy environments.

Experimental realization of two-dimensional single-layer ultracold gases of ^(87)Rb in an accordion lattice

We experimentally realize two-dimensional(2D) single-layer ultracold gases of ^(87)Rb by dynamically tuning the periodicity of a standing wave, known as accordion lattice. In order to load ^(87)Rb Bose-Einstein condensate into single dark fringe node of the blue detuning optical lattice, we reduce the lattice periodicity from 26.7 μm to 3.5 μm with the help of an acousto-optic deflector(AOD) to compress the three-dimensional BEC adiabatically into a flat and uniform quasi-2D single-layer. We describe the experimental procedure of the atoms loading into the accordion lattice in detail and present the characteristics of the quasi-2D ultracold gases. This setup provides an important platform for studying in-and out-of equilibrium physics, phase transition and 2D topological matter.

Rydberg electromagnetically induced transparency in^(40)K ultracold Fermi gases

We report the measurement of the electromagnetically induced transparency(EIT)with Rydberg states in ultracold^(40)K Fermi gases,which is obtained through a two-photon process with the ladder scheme.Rydberg–EIT lines are obtained by measuring the atomic losses instead of the transmitted probe beam.Based on the laser frequency stabilization locking to the superstable cavity,we study the Rydberg–EIT line shapes for the 37s and 35d states.We experimentally demonstrate the significant change in the Rydberg–EIT spectrum by changing the principal quantum number of the Rydberg state(n=37/52 and l=0).Moreover,the transparency peak position shift is observed,which may be induced by the interaction of the Rydberg atoms.This work provides a platform to explore many interesting behaviors involving Rydberg states in ultracold Fermi gases.