Bulletin of the American Physical Society
48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017; Sacramento, California
Session B5: Atomic and Molecular Structure |
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Chair: Jim Babb, ITAMP Room: 310 |
Tuesday, June 6, 2017 10:30AM - 10:42AM |
B5.00001: Closed-channel fraction of a strongly interacting Fermi Gas. Xiang-Pei Liu, Hao-Ze Chen, Xing-Can Yao, Xiao-Qiong Wang, Yu-Xuan Wang, Yu-Ping Wu, Qi-Jin Chen, Yu-Ao Chen, Jian-Wei Pan Near a Feshbach resonance, the many-body state of paired atoms is the so-called dressed molecule which can be understood as a linear combination of open-channel atom pairs and closed-channel bare molecules. The closed-channel fraction plays a crucial role in the description of the BEC-BCS crossover since it quantifies the mixing between the atom pairs and the bare molecules. In this presentation, I will first show the experimental procedure for producing of large degenerate Fermi gas. With advanced laser cooling and sympathetic cooling, we are able to obtain a maximum molecule number of 3×10$^{\mathrm{6}}$ at T/T$_{\mathrm{F}}$\textasciitilde 0.06. The low temperature and large atom number allow us to study the closed-channel fraction over a wide parametric range (scattering length, fermi momentum and temperature). With a molecule probe laser, we are able to extract the closed-channel fraction in the BEC-BCS crossover. Experimental results show a good agreement with the prediction of two-channel model. [Preview Abstract] |
Tuesday, June 6, 2017 10:42AM - 10:54AM |
B5.00002: Weak values of spin and momentum in atomic systems. Robert Flack, Basil Hiley, Peter Barker, Vincenzo Monachello, Joel Morley Weak values have a long history and were first considered by Landau and London in connection with superfluids. Hirschfelder called them sub-observables and Dirac anticipatied them when discussing non-commutative geometry in quantum mechanics. The idea of a weak value has returned to prominence due to Aharonov, Albert and Vaidman showing how they can be measured. They are not eigenvalues of the system and can not be measured by a collapse of the wave function with the traditional Von Neumann (strong) measurement which is a single stage process. In contrast the weak measurement process has three stages; preselection, weak stage and finally a post selection. Although weak values have been observed using photons and neutrons, we are building two experiments to observe weak values of spin and momentum in atomic systems. For spin we are following the method outlined by Duck et al which is a variant on the original Stern-Gerlach experiment using a metastable, $\rm 2^{3}S_{1}$, form of helium. For momentum we are using a method similar to that used by Kocsis with excited argon atoms in the $\rm ^{3}P_{2}$ state, passing through a 2-slit interferometer. The design, simulation and re [Preview Abstract] |
Tuesday, June 6, 2017 10:54AM - 11:06AM |
B5.00003: Finding frustrations and topological phases in a quasi-1D zig-zag chain of dipoles Niraj R. Ghimire, Susanne F. Yelin The goal is to investigate frustrations that lead to interesting phases in a one-dimensional zig-zag chain of dipoles. This type of system could potentially be modeled by ultracold polar molecules, and be extended such that topological quantities in triangular or hexagonal lattices can be studied. To do so, we take into account the nearest-neighbor (NN) and next-nearest-neighbor (NNN) hopping and interactions and find the ground state of the spin $S=1/2$ model by using the Density Matrix Renormalization Group (DMRG) method. [Preview Abstract] |
Tuesday, June 6, 2017 11:06AM - 11:18AM |
B5.00004: Non-Perturbative Calculation and Measurement of Strong Light Shifts with Floquet Theory Simon Coop, Silvana Palacios, Pau Gomez, Morgan W. Mitchell We describe a new theory for calculating atomic light shifts (ac Stark shifts) using Floquet's theorem, and we present spectroscopic data verifying our calculations. The theory remains accurate in the presence of strong level-mixing where the shifts are larger than the hyperfine splitting, and can quantitatively describe shifts due to multiple wavelengths with arbitrary polarization. As the theory can be used to accurately predict large nonlinear shifts, it could be useful for measuring electric-dipole matrix elements. This has implications for optical clocks, tests of atomic structure calculations, and fundamental atomic physics. This theory could also be useful for site-dependent state preparation in quantum simulators, and general experiment design and characterization. [Preview Abstract] |
Tuesday, June 6, 2017 11:18AM - 11:30AM |
B5.00005: Developing Potential Energy Curves of Acidic and Basic Amino Acids Using Quantum Computational Techniques C.P. De Guzman, M. Andrianarijaona, Y. Yoshida, K. Kim, V.M. Andrianarijaona Proteins are made out of long chains of amino acids and are an integral part of many tasks of a cell. Because the function of a protein is caused by its structure, even minute changes in the molecular geometry of the protein can have large effects on how the protein can be used. This study investigated how manipulations in the structure of acidic and basic amino acids affected their potential energy. Acidic and basic amino acids were chosen because prior studies have suggested that the ionizable side chains of these amino acids can be very influential on a molecule's prefered conformation. Each atom in the molecule was pulled along x, y, and z axis to see how different types of changes affect the potential energy of the whole structure. The results of our calculations, which were done using ORCA, emphasize the vibronic couplings. The aggregated data was used to create a data set of potential energy curves to better understand the quantum dynamic properties of acidic and basic amino acids (preliminary data was presented in http://meetings.aps.org/Meeting/MAR16/Session/M1.273 andhttp://meetings.aps.org/Meeting/FWS16/Session/F2.6). [Preview Abstract] |
Tuesday, June 6, 2017 11:30AM - 11:42AM |
B5.00006: Topological spin-charge separation in one dimensional optical superlattices Haiping Hu, Chuanwei Zhang Spin-charge separation is a hallmark phenomenon of 1D strongly interacting systems. However, whether spin and charge excitations in strong interacting region can possess non-trivial topological properties has not been explored. Here we show that topological spin-charge separation can be realized using ultracold fermions in a 1D optical superlattice. We demonstrate the emergence of topological magnetic excitations in a wide interaction regime through numerical density matrix renormalization group (DMRG) study. Such topological states are protected by a finite magnon excitation gap and characterized by gapless magnon edge state excitations. The magnon excitations can be quantized pumped between edges by adiabatically tuning the superlattice phases, realizing topological magnon pumping. [Preview Abstract] |
Tuesday, June 6, 2017 11:42AM - 11:54AM |
B5.00007: Spectroscopic studies of the ground state dissociation energy and isotope shift of NaD Chin-Chun Tsai, Chia-Ching Chu, Yin-Ji Li, Rong-Sin Lin, Wei-Fung He, Thou-Jen Whang We report a spectroscopic measurement of the NaD X$^1\Sigma^+$ ground state dissociation energy and its isotope shift. Stimulated emission pumping with fluorescence depletion spectroscopy is applied to measure the rovibrational levels of the near-dissociation region. A total of 230 rovibrational levels in the range of $9\leq v'' \leq29$ and $1\leq J'' \leq11$ are observed and the highest vibrational level $v'' = 29$ is about 50 cm$^{-1}$ to the dissociation limit. Analyzing the highest 5 vibrational levels yields the dissociation energy $D_e$ =15822 $\pm$ 5 cm$^{-1}$ with $v_D$ = 31.2 $\pm$ 0.1. With our previous study, we are able to determine the difference in the well depths of this isotopologues, $D_e$ = $D_e$(NaH) - $D_e$(NaD) = -7 cm$^{-1}$. [Preview Abstract] |
Tuesday, June 6, 2017 11:54AM - 12:06PM |
B5.00008: Proposal of a Robust Quantum Switch with Rydberg excitations Jing Qian Depending on a Y-typed level configuration of atoms, we develop a scheme of efficiently switching Rydberg excitations between two Rydberg states via opening or closing the intrastate interaction on the strongly-coupled Rydberg state (the other Rydberg state is weakly-coupled). When such interaction is open, a large number of atoms will be counterintuitively excited to the weakly-coupled state, rather than the strongly-coupled state as in the case of that interaction is closed. By systematically investigating relevant parameters we find the scheme is quite robust and very insensitive to the intrastate interaction on the weakly-coupled state, the spontaneous decay rate of middle excited state, and the duration time of conversion. Moreover, we simulate a switching cycle under realistic experimental parameters and find the single Rydberg excitations can indeed be switched in which the switch efficiency reaches as high as 0.92. This scheme may serve as a new route to the selective excitations with multiple Rydberg states, enabling new applications in developing various quantum devices. [Preview Abstract] |
Tuesday, June 6, 2017 12:06PM - 12:18PM |
B5.00009: On the computations of decay widths of Fano resonances Tsveta Miteva, S\'{e}van Kazandjian, Nicolas Sisourat We present a novel approach to the calculation of decay widths of Fano resonances in singly-ionized systems. In our approach, the bound part of the resonance is approximated at the zeroth order as a one-hole configuration. The final states of the decay are obtained after diagonalization of the Hamiltonian matrix in the space of all two-hole-one-particle (2h1p) configurations with a fixed virtual orbital. The Fano-CI method can be applied to the computation of both total and partial decay widths. Furthermore, it has fairly low computational costs and can thus be employed for investigating medium-sized atomic and molecular systems. To check the validity of our method, we carried out benchmark calculations of Auger and ICD widths of small rare-gas and hydrogen-bonded clusters. Comparison with available theoretical and experimental data shows that a satisfactory estimate of the decay width can be achieved with a relatively small basis set, which is of importance for the application of the method to larger systems. [1] [1] T. Miteva, S. Kazandjian and N. Sisourat, accepted in Chem. Phys. (2016) [Preview Abstract] |
Tuesday, June 6, 2017 12:18PM - 12:30PM |
B5.00010: Focusing of Rydberg Ps atoms using an electrostatic mirror with minimal chromatic aberration Adric Jones, J. Moxom, H. J. Rutbeck-Goldman, K. A. Osorno, G. G. Cecchini, M. Fuentes-Garcia, D. J. Adams, R. G. Greaves, H. W. K. Tom, A. P. Mills, Jr. We present experimental measurements demonstrating the electrostatic focusing of point source of Rydberg Ps atoms to a 30~mm spot on a position sensitive detector 6~m away, using a novel mirror design that is very nearly free of chromatic aberrations. The mirror is composed of 360 wires, 1~mm in diameter, arranged to form a truncated oblate cylindrical surface. Alternating positive and negative potentials are applied to neighboring wires, producing a radial electric field $\leq 10^5$~V/m which diminishes exponentially. We see an increase in the signal rate of a factor of $7 \pm 1$, about 2.8 times smaller than the geometric ratio of the mirror collection area to that of the detector. This apparent deviation from the expected efficiency is understood to result from two systematic effects: (1) the angular range of excitation accessible with the UV laser bandwidth on resonance, and (2) the difficulty in producing Rydberg Ps in low-field seeking Stark states (\emph{i.e.}, those of $k > 0$). \newline{} Using a mirror of similar design with an optical quality finish, it would be possible to make a measurement of the gravitational deflection of antimatter in Earth's field to a precision of about 1\%. [Preview Abstract] |
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