Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session R5: Feshbach Resonances |
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Chair: Seth Aubin, College of William and Mary Room: Clark Hall 107 |
Friday, May 22, 2009 10:30AM - 10:42AM |
R5.00001: Feshbach Resonances in Ultracold Gases Eite Tiesinga, Cheng Chin, Rudolf Grimm, Paul Julienne Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. They have found numerous experimental applications, opening up the way to important breakthroughs. This Review broadly covers the phenomenon of Feshbach resonances in ultracold gases and their main applications. This includes the theoretical background and models for the description of Feshbach resonances, the experimental methods to find and characterize the resonances, a discussion of the main properties of resonances in various atomic species and mixed species systems, and an overview of key experiments with atomic Bose-Einstein condensates, degenerate Fermi gases, and ultracold molecules. This Review has been submitted to Reviews of Modern Physics. [Preview Abstract] |
Friday, May 22, 2009 10:42AM - 10:54AM |
R5.00002: Tuning atomic interactions near a Feshbach resonance in 87Rb Robert Compton, Yu-Ju Lin, Karina Jiminez-Garcia, Ian Spielman The ability to tune the scattering length for collisons in ultracold gases is currently enabling the investigation of many- body Hamiltonians, such as the Bose-Hubbard model. For $^{87} $Rb, the strongest resonance is at 1007.4 G and is only $\approx$~200 mG in width. Precise control of scattering length therefore requires field resolution of 10 ppm. Here we demonstrate field resolution approaching 10 ppm with negligible drift on a timescale of 10 s, despite the dissipation of 12 kW of Joule heating in the field coils. We measure the three body loss rate constant K3 as a function of field in close proximity to the resonance, along with the the scattering length. In addition, using rf association, we map the binding energy for Feshbach molecules on the low field side of the resonance. Finally, we use rf to mix molecular levels near the resonance, and investigate how this changes the character of the resonance, potentially easing contraints on field response for tunability of the scattering length. [Preview Abstract] |
Friday, May 22, 2009 10:54AM - 11:06AM |
R5.00003: Analytic descriptions of magnetic Feshbach resonances in nonzero partial waves Bo Gao We present analytic descriptions of atomic interaction and pairing at ultracold temperatures with emphasis on magnetic Feshbach resonances in nonzero partial waves. Formulas will be presented both for the binding energies below the threshold and for the Feshach/shape resonances above the threshold. The results are derived from the quantum-defect theory and are applicable to both broad and narrow Feshbach resonances, the differences of which will be rigorously defined. We will also introduce a generalized scattering length that is well defined and useful for all partial waves, to replace the traditional definition that fails for $l\ge 2$ due to the long-range van der Waals interaction. [Preview Abstract] |
Friday, May 22, 2009 11:06AM - 11:18AM |
R5.00004: Controlling a magnetic Feshbach resonance with laser light Matthias Lettner, Dominik Bauer, Christoph Vo, Gerhard Rempe, Stephan Duerr The capability to tune the strength of the elastic interparticle interaction is crucial for many experiments with ultracold gases. Magnetic Feshbach resonances are a tool widely used for this purpose, but future experiments would benefit from additional flexibility such as spatial modulation of the interaction strength on short length scales. Optical Feshbach resonances offer this possibility in principle, but suffer from fast particle loss due to light-induced inelastic collisions. Here we show that light near-resonant with a molecular bound-to-bound transition can be used to shift the magnetic field at which a magnetic Feshbach resonance occurs. This makes it possible to tune the interaction strength with laser light and at the same time induce considerably less loss than an optical Feshbach resonance would do. For small detuning from the bound-to-bound transition we observe a splitting of the Feshbach resonance similar to an Autler-Towns doublet. [Preview Abstract] |
Friday, May 22, 2009 11:18AM - 11:30AM |
R5.00005: Observation of an Optical Feshbach Resonance in $^{88}$Sr P.G. Mickelson, Y.N. Martinez de Escobar, M. Yan, R. Chakraborty, T.C. Killian We have observed an optical Feshbach resonance (OFR) using the narrow intercombination line in $^{88}$Sr. As suggested by Ciurylo et. al [Phys. Rev. A 71, 030701(R) (2005)], the scattering wave function is changed by applying an additional laser to the trapped atom sample and varying its intensity and detuning from a molecular level near the intercombination line transition. We use the change in the rate of thermalization of atoms as our diagnostic and a model of evaporation to determine the corresponding scattering length. While the change in scattering length due to the OFR is accompanied by modest losses, the decreased sample temperature leads to a slight increase in the phase space density of the sample. Demonstration of the OFR without large atom loss offers fine control of the properties of the atomic system. [Preview Abstract] |
Friday, May 22, 2009 11:30AM - 11:42AM |
R5.00006: Optical Feshbach resonances in 171Yb Iris Reichenbach, Paul S. Julienne, Ivan H. Deutsch Feshbach resonances are a central tool in quantum control of many-body atomic systems. While magnetically induced resonances are routinely implemented in many gases of alkali atoms, optical Feshbach resonances have long been elusive owing to the fact that the optical transition is relatively broad and not easily resolved. We show that alkaline-earth-like atoms are much better suited for the implementation of optical Feshbach resonances, due to their very narrow ${}^1S_0 \rightarrow {}^3P_1$ intercombination transition. We model the optical Feshbach resonance on the example of 171Yb and determine the scattering length for different detunings and temperatures. We include nuclear spin and hyperfine interaction which leads to purely-long range states and the possibility of manipulating nuclear spin coherence for applications in quantum information processing. [Preview Abstract] |
Friday, May 22, 2009 11:42AM - 11:54AM |
R5.00007: Shape effects in low energy Feshbach resonances Ryan Kalas, Eddy Timmermans We study finite interaction range effects in two-body collisions of ultra-cold, neutral atoms near a magnetically controlled, low energy Feshbach resonance. The finite range of the inter-particle interactions gives rise to a characteristic momentum dependence of the scattering amplitude that is traditionally described by the effective range expansion. The coupled channel Feshbach resonance gives an effective range that varies as the magnetic field sweeps through the resonance and that diverges near the the zero-crossing point (corresponding to the magnetic field value of vanishing scattering length). To describe the interactions near the zero-crossing point, we propose an effective potential expansion to replace the expansion of the effective range. The model in which we work assumes an interaction potential in the open channel that is a separable potential, which allows analytical calculations for arbitrary interaction strengths. The results reveal important general trends and suggest a greatly simplified description of a narrow Feshbach resonance in terms of the magnetic-field shifted scattering length. [Preview Abstract] |
Friday, May 22, 2009 11:54AM - 12:06PM |
R5.00008: Stability of a Three-Component $^{6}$Li$^{40}$K Fermi Mixture near a $^{6}$Li Feshbach Resonance Devang Naik, Frederik Spiegelhalder, Andreas Trenkwalder, Erik Wille, Gerhard Hendl, Florian Schreck, Rudolf Grimm We report on the stability of a three-component Fermi gas consisting of a strongly interacting $^{6}$Li two-component degenerate mixture near the 834-G Feshbach resonance in the presence of a weakly interacting $^{40}$K sample. Despite the presence of three distinguishable particles, we observe stability against three-body recombination both on resonance and on the BCS side of the resonance. On the molecular side, however, we observe increasing losses due to atom-dimer collisions. We have measured the corresponding rate coefficients, along with Li-K thermalization rates, for different magnetic fields around the resonance. The observed stability and thermalization opens up the possibility of using $^{40}$K as a probe to study $^{6}$Li BEC-BCS crossover dynamics. [Preview Abstract] |
Friday, May 22, 2009 12:06PM - 12:18PM |
R5.00009: Atom loss in a two-component Fermi gas near a Feshbach resonance Gyu-Boong Jo, Jae H. Choi, Caleb A. Christensen, Ye-ryoung Lee, Tout Wang, Tony H. Kim, Wolfgang Ketterle, David E. Pritchard We present our recent progress on the study of the inelastic atom loss in a two-component ${ }^6Li$atoms near a Feshbach resonance at 834G. A degenerate${ }^6Li$atoms in the lowest two hyperfine states are prepared in an optical dipole trap after sympathetic cooling with bosonic ${ }^{23}Na$ atoms. The magnetic field is rapidly ramped up to a Feshbach resonance, and the inelastic atom loss is monitored. The rapid ramp-up of the magnetic fields offers the opportunity to study the non-equilibrium situation and the time-dependence of atom-atom correlations. We have tried to map out the atom loss in a cold Lithium gas as a function of magnetic field and the temperature. We present current experiments revealing the non-monotonic behavior which has been observed in preliminary experiments. [Preview Abstract] |
Friday, May 22, 2009 12:18PM - 12:30PM |
R5.00010: Electronic Feshbach Resonances created in Soft X-ray--Induced O$_{2}$ dissociation Etienne Gagnone, Robin Santra, Arvinder Sandhu, Vandana Sharma, Wen Li, Phay Ho, Predrag Ranitovic, Lew Cocke, Craig Hogle, Margaret Murnane, Henry Kapteyn When an atom or molecule is ionized by an x-ray, super-excited states can be created that then decay, or autoionize, by ejecting a second electron from the ion. Here we find that autoionization following soft x-ray photoionization of molecular oxygen follows a complex, multi-step, process[1]. By interrupting the autoionization process using a short laser pulse, we show that autoionization cannot occur until the internuclear separation of the fragments is greater than 30~{\AA}ngstroms. As the ion and excited neutral atom separate, we directly observe the birth of a new state. We follow the transformation of electronically bound states of the molecular ion into Feshbach resonances of the neutral oxygen atom that are characterized by both positive and negative binding energies. States with negative binding energies have not been predicted or observed in neutral atoms previously. 1. A. Sandhu et al., ``Observing the birth of electronic Feshbach resonances in soft x-ray induced O$_{2}$ dissociation,'' Science 322, 1081 (2008). [Preview Abstract] |
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