Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session H26: Few-Body, Molecular, and Long-Range Interacting Systems |
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Sponsoring Units: DAMOP Chair: Yuval Baum, Caltech Room: LACC 404A |
Tuesday, March 6, 2018 2:30PM - 2:42PM |
H26.00001: One--particle Effective Potential for Helium Atom Charles Weatherford, Daniel Gebremedhin A single-particle pseudo--potential that splits the effect of the electron--electron repulsive potential of Helium (He) atom into two non--interacting identical particle potentials is numerically computed. This is done by minimizing the expectation value of the difference between the approximate and exact Hamiltonians over the Hilbert space of He atom. The one--particle potential is expanded in a spatial basis--set which leads to an overdetermined system of linear equation that was solved using a least square approximation. The method involves a self--consistent iterative scheme where a converged solution valid for any state of the atom can be calculated. The total ground state energy for these two non--interacting particles under the calculated potential is found to be -2.861 68, which is the Hartree--Fock limit for the He atom. |
Tuesday, March 6, 2018 2:42PM - 2:54PM |
H26.00002: Controlling Electron-electron Correlation in Frustrated Double Ionization of Triatomic Molecules with Orthogonally Polarized Two-color Laser Fields Ahai Chen, Matthias Kling, Agapi Emmanouilidou We demonstrate the control of electron-electron correlation in frustrated double ionization (FDI) of the two-electron triatomic molecule D_{3}^{+} when driven by two orthogonally polarized two-color laser fields. We employ a three-dimensional semiclassical model that fully accounts for the electron and nuclear motion in strong fields. We analyze the FDI probability and the distribution of the momentum of the escaping electron along the polarization direction of the longer wavelength and more intense laser field. These observables, when considered in conjunction, bear clear signatures of the prevalence or absence of electron-electron correlation in FDI, depending on the time delay between the two laser pulses. |
Tuesday, March 6, 2018 2:54PM - 3:06PM |
H26.00003: Experimental Observation of Molecular Rotations Stimulated by Optical Magnetic Forces M. Tuan Trinh, Krishnandu Makhal, Elizabeth Dreyer, Stephen Rand Conventionally, the interaction of the magnetic field of light with materials is ignored since most materials have low magnetic susceptibilities. However, in the high field, magneto-electric interactions can cause enhanced magnetic dipole scattering. Enhanced magnetization in homogeneous dielectrics is of fundamental importance to high-frequency magnetism. We report optically induced magnetization and stimulated librations at the molecular level in liquid CCl_{4}, SiCl_{4}, Si(OCH_{3})_{4}, and Si(OC_{2}H_{5})_{4} and compare results with a quantum theory which analyzes the conversion of orbital angular momentum to molecular rotation via optical magnetic torque[1]. The inter-conversion of angular momenta increases the effective area enclosed by polarization currents governing magnetic response. Our results are the first observations of Stokes-shifted librations and vibrations driven by femtosecond magneto-electric interactions in tetrahalides and strongly support a torque-mediated mechanism. |
Tuesday, March 6, 2018 3:06PM - 3:18PM |
H26.00004: Creation of ultracold molecules within the lifetime scale by direct implementation of an optical frequency comb Gengyuan Liu, Svetlana Malinovskaya A method is proposed to create molecules in the ultracold state from the Feshbach molecules by stepwise adiabatic passage using an optical frequency comb without losses due to decoherence. An emphasis is made on the impact of the vibrational state manifold on controllability of the coherent dynamics by including five excited states into the model. The results are compared with recently reported results on a three-level lambda system. Sinusoidal modulation across an individual pulse in the pulse train is applied, leading to the creation of a quasi-dark state, which minimizes population of the transitional, vibrational state manifold and efficiently mitigates decoherence in the system. The parity of the temporal chirp is shown to be an important factor in designing population dynamics in the system. |
Tuesday, March 6, 2018 3:18PM - 3:30PM |
H26.00005: From few- to many-body quantum physics Marco Tavora, Mauro Schiulaz, Lea Santos Experiments with cold atoms can be performed with a controllable number of particles, which motivates exploring how quantum systems transition from being few-body to becoming many-body. Taking the half-filling case as a reference to the many-body limit, we investigate how static and dynamic properties of one-dimensional quantum systems approach this limit as the number N of particles increases from 1. Our results indicate that for N as small as 4, several properties seem already very similar to those observed at half-filling. Before reaching this point, however, the results are highly dependent on N. |
Tuesday, March 6, 2018 3:30PM - 3:42PM |
H26.00006: Two-Point Momentum and Spatial Correlations of Few Ultracold Quasi-One-Dimensional Trapped Fermions: Diffraction Patterns Benedikt Brandt, Constantine Yannouleas, Uzi Landman Spatial and momentum correlations are important in the analysis of the quantum states and different phases of trapped ultracold atom systems as a function of the strength of interatomic interactions. Identification and understanding of spin-resolved patterns exhibited in two-point correlations are key for uncovering the symmetry and structure of the many-body wavefunctions of the trapped system. Using the full configuration interaction method for diagonalization of the many-body Hamiltonian with 2 to 4 fermionic atoms trapped in single or multiple wells, we analyze two-point spatial and momentum space correlations and noise distributions, for a broad range of interparticle contact repulsion strengths and interwell separations, unveiling characteristics allowing insight into the transition from the intermediate quasi BEC regime to the strong-repulsion Tonks-Giradeau (TG) phase. The ab-initio numerical predictions agree well with those from our analytical model. The two-point momentum correlation is found to exhibit damped oscillatory diffraction behavior, which fully develops for atoms trapped in a single well with strong interatomic repulsion in the TG regime, or for atoms in well-separated multi-well traps [arXiv:1710.07853] . |
Tuesday, March 6, 2018 3:42PM - 3:54PM |
H26.00007: Towards simulating many-body quantum dynamics with strontium atoms in optical tweezers Alexandre Cooper, Jacob Covey, Ivaylo Madjarov, Zeren Lin, Brian Timar, Alexander Baumgartner, Nicholas Redd, Emily Qiu, Dan Ilyin, Manuel Endres Ultracold atoms in optical tweezers provide a versatile platform for simulating interacting many-body quantum systems. The ability to assemble single atoms in various spatial configurations, selectively address and control their quantum states, and introduce long-range interactions between them enables studying complex Hamiltonians that are otherwise difficult to access. We describe our progress in assembling strontium atoms in two-dimensional arrays of optical tweezers with tunable Rydberg interactions. Our work offers promising research avenues for studying non-equilibrium dynamics of disordered systems, realizing novel states of matter, and simulating spin models with tunable parameters. |
Tuesday, March 6, 2018 3:54PM - 4:06PM |
H26.00008: Enhancing Kondo Coupling in Alkaline-Earth Atomic Gases with Confinement-induced Resonances in Mixed Dimensions Yanting Cheng, Ren Zhang, Peng Zhang, Hui Zhai The Kondo effect describes the spin-exchanging interaction between localized impurity and itin- erant fermions. The ultracold alkaline earth atomic gas provides a natural platform for quantum simulation of the Kondo model, utilizing its long-lived clock state and the nuclear-spin exchanging interaction between clock state and ground state. One of the key issue now is whether the Kondo temperature can be high enough to be reached in current experiment, for which we have proposed using a transverse confinement to confine atoms into a one-dimensional tube and to utilize the confinement-induced resonance to enhance the Kondo coupling. In this work, we further consider the 1 + 0 dimensional scattering problem when the clock state is further confined by an axial har- monic confinement. We show that this axial confinement for the clock state atoms not only plays a role for localizing them, but also can act as an additional control knob to reach the confinement- induced resonance. We show that by combining both the transverse and the axial confinements, the confinement-induced resonance can be reached in the practical conditions and the Kondo effect can be attainable in this system. |
Tuesday, March 6, 2018 4:06PM - 4:18PM |
H26.00009: Atomic Entanglements in Three-Body Molecular Dissociation, Peter Langhoff, Jeffrey Mills, Jerry Boatz Theoretical studies are reported of atomic state entanglements in the three-body dissociation of molecules employing tri-atomic hydrogen (H3) as a prototypical example. The predictions made employ methods based on orthonormal outer-products of atomic eigenstates, providing a separable Hilbert space in support of totally antisymmetric solutions of the molecular Schr\"odinger equation. Adiabatic Born-Oppenheimer molecular energies are obtained in the form of sums of the energies of the individual atomic constituents and of their pairwise interactions. Detailed descriptions of the electronic states of constitute atoms within a molecule are provided which allows predictions of atomic entanglements upon dissociation in cases involving at least one internally excited atom. Energy sharing among the three atoms gives rise to complex fractional populations of ground and excited atomic states consequent of the congestion and degeneracy of atomic spectra, which entanglements are accessible to measurement under coherent dissociation conditions. These possibilities are described in detail in the particular cases of symmetric collinear and C3v dissociations, providing specific potential sources for experimental formation and trapping methodologies and related information theory applications. |
Tuesday, March 6, 2018 4:18PM - 4:30PM |
H26.00010: Enhanced Fractal Dynamics of a BEC Induced by Dipolar Interactions. Jessica Taylor, Boaz Ilan, Kevin Mitchell Of current interest is the ability to stabilize a BEC. Earlier studies show that various configurations of the Nonlinear Schrödinger equation effect the flux / escape rate of a BEC. We extend these studies to the defocusing NLS equation with dipolar interactions. Here, we consider the effects of a attractive dipolar potential on the fractal escape-rates of a BEC with repulsive short-range atom-atom interactions relative to a dipolar ground state initial condition. We conclude that the addition of dipolar effects reduces the dispersion of the system and arrests collapse of representative wavefunction. |
Tuesday, March 6, 2018 4:30PM - 4:42PM |
H26.00011: Observation of Regular Energy Patterns in Finite Systems of Low-Dimensional Ionic Crystals Philip Thomas, Scott Rossel, Shawn Smith, Orion Ciftja Invention of novel nanofabrication techniques has made possible the realization of stable finite systems of almost perfect low-dimensional ionic crystals consisting of regular arrays of alternating positive and negative ions. For example, it has been successfully demonstrated that certain cations and ions can be trapped and aligned alternately inside a carbon nanotube forming a nearly ideal finite one-dimensional ionic crystal. In this work we consider a simple model of a finite one-dimensional ionic crystal and study its properties. We calculate the energy for ion for various finite systems consisting of an arbitrary number of ions that interact with a standard Coulomb interaction potential. The results give a fairly accurate picture of how the energy of this finite one-dimensional ionic crystal evolves towards the bulk value as the size of the system increases. The results obtained show some interesting regular patterns of the energy per ion as a function of the parity (even or odd) of the total number of ions in the crystal. Possible extensions of this approach to other finite low-dimensional ionic crystals are discussed. |
Tuesday, March 6, 2018 4:42PM - 4:54PM |
H26.00012: Reverse engineering approach for controlling the spin dynamics Qi Zhang, Xi Chen, David Guéry-Odelin In a reverse engineering protocol, one sets the evolution of the spin variables and infer the time evolution of the magnetic components. The solution is not unique, and therefore there are many classes of solutions depending on the analytical formulation of the problem that has been considered. I will illustrate this feature using three different formulations of the same problem. |
Tuesday, March 6, 2018 4:54PM - 5:06PM |
H26.00013: Creation energy of ionic defects in water ice studied with diffuse neutron scattering David Jonathan Morris, Konrad Siemensmeyer, Jens-Uwe Hoffmann, Illya Glavatskyi, Bastian Klemke, David Tennant, Sergei Isakov, Roderich Moessner Water is one of nature’s most familiar materials yet it is also one of the most unusual. From lowering its density upon freezing to being an almost universal solvent there are many properties that are peculiar to water. In its solid phase the oxygen ions sit at well-ordered crystalline sites with hydrogen ions sitting at one-of-two possible sites between neighboring oxygen. The structural configuration is described by the Bernal-Fowler “ice rules” where each oxygen bonds covalently with two nearby hydrogen ions and forms hydrogen-bonds with two further away hydrogen ions. By mapping the hydrogen displacement from the center of the O-O bond onto an Ising vector it has been shown that ice can be modelled using an emergent electromagnetic theory. Here we present diffuse neutron scattering results from heavy water ice, D_{2}O, that are fitted with a large-N electromagnetic model from Isakov et al. allowing us to find the correlation length between ionic defects in water ice, i.e. H_{3}O^{+} and OH^{-}, and from this deduce the formation energy of the defect pair. |
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