Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session Q07: Bose-Einstein condensates |
Hide Abstracts |
Chair: Aephraim Steinberg, University of Toronto Room: Wisconsin Center 103AB |
Thursday, May 30, 2019 2:00PM - 2:12PM |
Q07.00001: Towards a quantum degenerate gas of $^{48}$Ti Kayleigh Cassella, Scott Eustice, Dan Stamper-Kurn Titanium is fundamentally different from all the elemental atomic gases brought to quantum degeneracy to-date. Titanium’s lowest energy electronic configuration [Ar] $3d^2 4s^2$ yields a ground level $a^3F_2$ that is characterized by non-zero orbital angular momentum yet a magnetic moment equivalent to that of the alkali-atoms. Hence, titanium’s tensor polarizability supports anisotropic atom-light interactions, which can be implemented in a quantum degenerate gas that is free from the strong long-range dipolar interactions observed in systems of lanthanides. While a closed transition does not exist out of the ground state, a metastable state, $a^5F_5$ at 6843 cm$^{-1}$ with electronic configuration [Ar] $3d^3 4s$, has a spin-allowed transition to an excited energy level $y^5G^0_6$ ([Ar] $3d^3 4p$) at 498.1713 nm. Existing spectroscopic data support the feasibility of laser-cooling and magneto-optical trapping (MOT); this transition is both closed and broad ($\Gamma= 2\pi\times 10.51$ MHz). We discuss the cooling and trapping scheme already underway: a spin-flip Zeeman slower followed by a MOT. We report on experimental progress towards a trapped, Doppler temperature gas of bosonic $^{48}$Ti, the most abundant isotope, and future plans to achieve quantum degeneracy. [Preview Abstract] |
Thursday, May 30, 2019 2:12PM - 2:24PM |
Q07.00002: Semiclassical Mean-Field Equations for Photon Bose-Einstein Condensates Enrico Stein, Axel Pelster In recent years the phenomenon of non-equilibrium Bose-Einstein condensation (BEC) has been studied extensively also within the realm of a Bose-Einstein condensate of photons. At its core this system consists of a dye solution filling a microcavity in which the photons are harmonically trapped. Due to cyclic absorption and reemission processes of photons the dye leads to a thermalisation of the photon gas at room temperature and finally to its Bose-Einstein condensation. Because of a non-ideal quantum efficiency, those cycles yield in addition a heating of the dye solution, which results in an effective photon-photon interaction. This talk focuses on the influences of the matter degrees of freedom on both the homogeneous photon BEC and the lowest-lying collective frequencies of the harmonically trapped photon BEC. In order to treat the matter, a modified semiclassical laser model is used. Following this track, the photon BEC is then described by an open-dissipative Gross-Pitaevskii equation, with a temporally retarded photon-photon interaction. The collective frequencies are worked out within a linear stability analysis. In the trapped case the analysis refers especially to the violation of the Kohn theorem, arising from the temporal non-locality of the thermo-optic interaction. [Preview Abstract] |
Thursday, May 30, 2019 2:24PM - 2:36PM |
Q07.00003: Faraday waves and granulation in a Bose-Einstein condensate Jason Nguyen, De Luo, Patrick Bagge, Randall Hulet Faraday waves are surface waves of a non-linear medium generated by parametric modulation of the medium. Faraday waves in a Bose-Einstein condensate have been created by periodically modulating the transverse confinement of an optical trap, which indirectly modulates the interactions\footnote{P. Engels, C. Atherton, \& M.~A. Hoefer, PRL 09, 095301 (2007)}. We have directly modulated the interactions via a Feshbach resonance in an elongated condensate of $^{7}\mathrm{Li}$ atoms in the $|1,1\rangle$ state and identify two distinct regimes, differing in modulation frequency and strength. For frequencies near, or twice the radial trap frequency and for weak modulation strengths, we generate Faraday waves which are well described by a mean-field theory that accounts for the $3$D nature of the elongated condensate. At lower frequencies no clear Faraday patterns occur, even with increasing modulation strength. Instead, the condensate forms an irregular granulated distribution that is outside the scope of a mean-field approach. In this regime, we find that the granulated condensate may be characterized by large quantum fluctuations and correlations, which are well-described using a beyond mean-field approach. [Preview Abstract] |
Thursday, May 30, 2019 2:36PM - 2:48PM |
Q07.00004: Filling-fraction dependent emission in a matter-wave emitter array Joonhyuk Kwon, Michael Stewart, Dominik Schneble Ultracold atoms in optical lattices realize a tunable open quantum system in the context of matter-wave emission into vacuum [1]. Previously, we observed deviations from single-particle dynamics in sparsely populated emitter arrays, due to atom reabsorption. Moreover, for arrays with large filling fractions, superradiant emission effects have been predicted [2]. We present an experimental investigation of the decay dynamics as a function of the filling fraction of the initial state in our optical lattice system. \newline \newline [1] L. Krinner, M. Stewart, A. Pazmiño, J. Kwon, D. Schneble, Spontaneous emission of matter waves from a tunable open quantum system, Nature 559, 589–592 (2018) \newline [2] de Vega, I., Porras, D. & Cirac, J. I. Matter-wave emission in optical lattices: single particle and collective effects. Phys. Rev. Lett. 101, 260404 (2008). [Preview Abstract] |
Thursday, May 30, 2019 2:48PM - 3:00PM |
Q07.00005: Rotational cooling of molecules in a BEC and angulon stability Martin Will, Tobias Lausch, Michael Fleischhauer We discuss the rotational cooling of diatomic molecules in a Bose-Einstein condensate (BEC) of ultra-cold atoms by emission of phonons with orbital angular momentum. Despite the superfluidity of the BEC there is no frictionless rotation for typical molecules since the dominant cooling occurs via emission of particle-like phonons. Only for macro-dimers, whose size become comparable or larger than the condensate healing length, a Landau-like, critical angular momentum exists below which phononemission is suppressed. We find that the angular momentum relaxation for usually sized molecules is much faster than the cooling of linear motion of impurities in a BEC. This also leads to a finite lifetime of angulons, quasi-particles of rotating molecules coupled to orbital angular-momentum phonons. The lifetimes are however still smaller than typical angulon binding energies. We are analyzing transition rates, between the angular-momentum states of the molecule, including single- and two-phonon scattering and discuss the effect of thermal phonons. [Preview Abstract] |
Thursday, May 30, 2019 3:00PM - 3:12PM |
Q07.00006: A Bose-Einstein condensate in a lattice produced by simultaneous Raman and RF coupling Sean Mossman, Thomas Bersano, Peter Engels Experiments with ultracold atoms allow for the generation of unique lattice structures probing advanced concepts from condensed matter and fundamental physics. Here, we experimentally demonstrate a spin-dependent, Galilean invariant lattice which emerges from the simultaneous application of Raman dressing and RF coupling. The Raman dressing explicitly breaks Galilean symmetry and produces linear spin-orbit coupling. When the RF coupling is added, Galilean symmetry is restored and a lattice structure emerges. With time-of-flight observations, we demonstrate key features of this novel lattice. [Preview Abstract] |
Thursday, May 30, 2019 3:12PM - 3:24PM |
Q07.00007: Tunneling Time of a Bose-Einstein condensate in a 1D atomic waveguide David Spierings, Ramon Ramos, Isabelle Racicot, Aephraim Steinberg We report on measurements of the tunneling time of Bose-condensed Rubidium~atoms in a one-dimensional system, tunneling through a 1-micron optical barrier. By localizing a pseudo-magnetic field inside the barrier and using the spin precession of the atoms to `clock' the time it takes for the atoms to pass through the classically forbidden region, we implement a Larmor measurement, as envisioned by Baz, Rybanchenko, and Buttiker [1,2,3,4]. In the limit that this measurement is `weak' (in the sense of Aharonov, Albert, and Vaidman), we are able to disentangle the back-action of the measurement from the inherent tunneling time. We measure a tunneling time of 0.62(7) milliseconds through our barrier. Our results show good agreement with theory and shed light onto this long-standing problem. [1] Baz', A. Lifetime of Intermediate States. \textit{Sov. J. Nucl. Phys. }4, 182 (1966).\textunderscore [2] Rybachenko, V. Time of Penetration of a Particle through a Potential Barrier. \textit{Sov. J. Nucl.} \textit{Phys. }5, 635 (1967). [\textunderscore 3] B\"{u}ttiker, M. Larmor precession and the traversal time for tunneling. \textit{Phys. Rev. B }27, 6178--6188 (1983). [4] Steinberg, A. M. Time and history in quantum tunneling. \textit{Superlattices and Microstructures}, \textit{23}(3--4), 823--832. (1998). \underline {http://doi.org/10.1006/spmi.1997.0543} [Preview Abstract] |
Thursday, May 30, 2019 3:24PM - 3:36PM |
Q07.00008: Weakly Interacting Bose Gas on a Sphere Natalia Moller, Vanderlei Bagnato, Axel Pelster Here we explore how to describe a weakly interacting Bose gas on a sphere. To this end we start with considering a radial harmonic trap, which confines the three-dimensional Bose gas in the vicinity of the surface of a sphere. Following the notion of dimensional reduction as outlined in Ref.~$^1$ we assume a large enough trap frequency so that the radial degree of freedom of the field operator is fixed despite of thermal and quantum fluctuations to the ground state of the radial harmonic trap and can be integrated out. With this we obtain an effective many-body field theory for a Bose-Einstein condensate on a quasi two-dimensional sphere, where the thickness of the cloud is determined self-consistently.\\ At first we determine the critical temperature of a Bose Gas on a sphere, where we recover in the limit of an infinitely large radius the case of a quasi two-dimensional plane with a vanishing critical temperature in accordance with the Mermin-Wagner theorem~$^2$. Afterwards, we analyze at zero temperature the mean-field physics of a Bose-Einstein condensate on a sphere by deriving the underlying time-dependent Gross-Pitaevskii equation. \\ ~$^1$ L. Salasnich et al., Phys. Rev. A {\bf 65}, 043614 (2002)\\ ~$^2$ N. Mermin and H. Wagner, Phys. Rev. Lett. {\bf 17}, 1133 (1966) [Preview Abstract] |
Thursday, May 30, 2019 3:36PM - 3:48PM |
Q07.00009: Spontaneously Created Attractive Bose-Einstein Condensates and Their Critical Behaviors Yiping Chen, Munekazu Horikoshi, Kosuke Yoshioka, Makoto Kuwata-Gonokami Bose-Einstein condensate (BEC) is a type of continuous phase transition. In general, when a continuous phase transition occurs on a finite timescale, it leads to defect and structure formation. This behavior is predicted to obey certain power law scaling in accordance to their universality class by the Kibble-Zurek mechanism. Experiments conducted in various system including repulsive BEC support this mechanism. However, the situation of attractive BEC remains ambiguous due to the lack of experimental observation. Here, we explore this phenomenon using a weakly attractive Bose gas with tunable interaction that is cooled by a fermionic coolant in an elongated trap. By controlling the timescale of the phase transition, we find that the gas subsequently forms a diverse number of bright solitons for attractive interaction and gray solitons for repulsive interaction. The power law scaling of the average soliton number over the timescale of the phase transition is measured. The results show that both attractive BEC and repulsive BEC obey the same power law scaling, which supports the idea of universality. [Preview Abstract] |
Thursday, May 30, 2019 3:48PM - 4:00PM |
Q07.00010: Detecting ionization fragments of ultracold quantum gases exposed to ultrashort laser pulses Philipp Wessels, Tobias Kroker, Mario Neundorf, Donika Imeri, Markus Drescher, Klaus Sengstock, Juliette Simonet Ultrashort laser pulses combined with ultracold quantum matter grant access to ultrafast time-scales and the possibility for controlled creation of ions and electrons in a quantum gas via strong-field ionization. Our dedicated quantum gas machine allows for simultaneous detection of charged ionization fragments and neutral atoms after an optical transport into a field-free region. Position sensitive high-speed micro-channel plate and phosphor screen detectors and simulations of the charged particle trajectories enable a mapping of the kinetic energies of the photoelectrons. We present first images of photoelectrons emitted out of a $^{87}$Rb Bose-Einstein condensate after strong-field ionization by ultrashort laser pulses of 215 fs duration. The confined interaction region consisting of a localized cloud of ultracold atoms and a focused femtosecond laser beam permits essentially background free measurements of ionization products emerging out of a source with negligible initial kinetic energy. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2022 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700