Magnetically tuned spin dynamics resonance

We present the experimental observation of a magnetically tuned resonance phenomenon resulting from spin mixing dynamics of ultracold atomic gases. In particular we study the magnetic field dependence of spin conversion in F=2 87Rb spinor condensates in the crossover from interaction dominated to quadratic Zeeman dominated dynamics. We discuss the observed phenomenon in the framework of spin dynamics as well as matter wave four wave mixing. Furthermore we show that the validity range of the single mode approximation for spin dynamics is significantly extended in the regime of high magnetic field

Measurement of a Mixed Spin Channel Feshbach Resonance in Rubidium 87

We report on the observation of a mixed spin channel Feshbach resonance at the low magnetic field value of (9.09 +/- 0.01) G for a mixture of |2,-1> and |1,+1> states in 87Rb. This mixture is important for applications of multi-component BECs of 87Rb, e.g. in spin mixture physics and for quantum entanglement. Values for position, height and width of the resonance are reported and compared to a recent theoretical calculation of this resonance.Comment: 4 pages, 3 figures minor changes, actualized citation

Ultracold quantum gases in triangular optical lattices

Over the last years the exciting developments in the field of ultracold atoms confined in optical lattices have led to numerous theoretical proposals devoted to the quantum simulation of problems e.g. known from condensed matter physics. Many of those ideas demand for experimental environments with non-cubic lattice geometries. In this paper we report on the implementation of a versatile three-beam lattice allowing for the generation of triangular as well as hexagonal optical lattices. As an important step the superfluid-Mott insulator (SF-MI) quantum phase transition has been observed and investigated in detail in this lattice geometry for the first time. In addition to this we study the physics of spinor Bose-Einstein condensates (BEC) in the presence of the triangular optical lattice potential, especially spin changing dynamics across the SF-MI transition. Our results suggest that below the SF-MI phase transition, a well-established mean-field model describes the observed data when renormalizing the spin-dependent interaction. Interestingly this opens new perspectives for a lattice driven tuning of a spin dynamics resonance occurring through the interplay of quadratic Zeeman effect and spin-dependent interaction. We finally discuss further lattice configurations which can be realized with our setup.Comment: 19 pages, 7 figure

Exact Solution of Strongly Interacting Quasi-One-Dimensional Spinor Bose Gases

We present an exact analytical solution of the fundamental system of quasi-one-dimensional spin-1 bosons with infinite delta-repulsion. The eigenfunctions are constructed from the wave functions of non-interacting spinless fermions, based on Girardeau's Fermi-Bose mapping, and from the wave functions of distinguishable spins. We show that the spinor bosons behave like a compound of non-interacting spinless fermions and non-interacting distinguishable spins. This duality is especially reflected in the spin densities and the energy spectrum. We find that the momentum distribution of the eigenstates depends on the symmetry of the spin function. Furthermore, we discuss the splitting of the ground state multiplet in the regime of large but finite repulsion.Comment: Revised to discuss large but finite interaction

Localization of bosonic atoms by fermionic impurities in a 3d optical lattice

We observe a localized phase of ultracold bosonic quantum gases in a 3-dimensional optical lattice induced by a small contribution of fermionic atoms acting as impurities in a Fermi-Bose quantum gas mixture. In particular we study the dependence of this transition on the fermionic 40K impurity concentration by a comparison to the corresponding superfluid to Mott insulator transition in a pure bosonic 87Rb gas and find a significant shift in the transition parameter. The observed shift is larger than expected based on a mean-field argument, which is a strong indication that disorder-related effects play a significant role.Comment: 4 pages, 4 figure

Do mixtures of bosonic and fermionic atoms adiabatically heat up in optical lattices?

Mixtures of bosonic and fermionic atoms in optical lattices provide a promising arena to study strongly correlated systems. In experiments realizing such mixtures in the quantum degenerate regime the temperature is a key parameter. In this work, we investigate the intrinsic heating and cooling effects due to an entropy-preserving raising of the optical lattice potential. We analyze this process, identify the generic behavior valid for a wide range of parameters, and discuss it quantitatively for the recent experiments with 87Rb and 40K atoms. In the absence of a lattice, we treat the bosons in the Hartree-Fock-Bogoliubov-Popov-approximation, including the fermions in a self-consistent mean field interaction. In the presence of the full three-dimensional lattice, we use a strong coupling expansion. As a result of the presence of the fermions, the temperature of the mixture after the lattice ramp-up is always higher than for the pure bosonic case. This sheds light onto a key point in the analysis of recent experiments.Comment: 5 pages, 3 figure

Optical frequency generation using fiber Bragg grating filters for applications in portable quantum sensing

A method for the agile generation of the optical frequencies required for laser cooling and atom interferometry of rubidium is demonstrated. It relies on fiber Bragg grating technology to filter the output of an electro-optic modulator and was demonstrated in a robust, alignment-free, single-seed, frequency-doubled, telecom fiber laser system. The system was capable of 50 ns frequency switching over a ~40 GHz range, ~0.5 W output power and amplitude modulation with a ~15 ns rise/fall time and an extinction ratio of 120 $\pm$ 2 dB. The technology is ideal for enabling high-bandwidth, mobile industrial and space applications of quantum technologies

Soliton trains in Bose-Fermi mixtures

We theoretically consider the formation of bright solitons in a mixture of Bose and Fermi degenerate gases. While we assume the forces between atoms in a pure Bose component to be effectively repulsive, their character can be changed from repulsive to attractive in the presence of fermions provided the Bose and Fermi gases attract each other strongly enough. In such a regime the Bose component becomes a gas of effectively attractive atoms. Hence, generating bright solitons in the bosonic gas is possible. Indeed, after a sudden increase of the strength of attraction between bosons and fermions (realized by using a Feshbach resonance technique or by firm radial squeezing of both samples) soliton trains appear in the Bose-Fermi mixture.Comment: 4 pages, 4 figure

Dynamics of F=2 Spinor Bose-Einstein Condensates

We experimentally investigate and analyze the rich dynamics in F=2 spinor Bose-Einstein condensates of Rb87. An interplay between mean-field driven spin dynamics and hyperfine-changing losses in addition to interactions with the thermal component is observed. In particular we measure conversion rates in the range of 10^-12 cm^3/s for spin changing collisions within the F=2 manifold and spin-dependent loss rates in the range of 10^-13 cm^3/s for hyperfine-changing collisions. From our data we observe a polar behavior in the F=2 ground state of Rb87, while we measure the F=1 ground state to be ferromagnetic. Furthermore we see a magnetization for condensates prepared with non-zero total spin.Comment: 4 pages, 2 figures, RevTe