Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session Q03: Fermi Gases |
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Chair: Meera Parish, Monash University Room: Grand B |
Thursday, May 31, 2018 8:00AM - 8:12AM |
Q03.00001: Dipole Oscillations of a BEC Immersed in a Degenerate Fermi Gas Brian DeSalvo, Krutik Patel, Geyue Cai, Cheng Chin For most ultracold atom experiments, the natural environment for a Bose-Einstein condensate (BEC) is vacuum. However, in a Bose-Fermi mixture, the BEC can be completely immersed inside of a degenerate Fermi gas. Interactions with such an environment can alter the dynamics and excitations of the BEC. We realize such a system by preparing a dual degenerate Bose-Fermi mixture of bosonic $^{133}$Cs and $^6$Li. Owing to the different quantum statistics of the particles as well as the large mass imbalance, the Cs BEC is much smaller than degenerate Fermi gas of Li and therefore is completely surrounded by fermions. To study the dynamics of this system, we excite a dipole oscillation of the Cs BEC. Taking advantage of an interspecies Feshbach resonance near 892 G, we study the effects of interactions on both the damping rate and frequency of the oscillation. For small scattering lengths, our results are well-described by mean-field theory. However, for large scattering lengths a number of surprising features are observed including a saturation in the damping rate and a non-linear dependence of the measured frequency shift. In this talk, we will present our results as well as our preliminary work on describing these unexpected features. [Preview Abstract] |
Thursday, May 31, 2018 8:12AM - 8:24AM |
Q03.00002: Energy Flow in a Two Temperature Fermi Gas Lorin Baird, Xin Wang, Stetson Roof, John Thomas We create a strongly interacting Fermi gas of $^{6}Li$ and divide it with a thin repulsive optical potential. Using Digital Micromirror Devices we also shape and modulate the repulsive optical potential to control the relative density and temperature of the two clouds. When the separating barrier is lowered the system is brought into contact. We plan to measure the thermal conductivity and diffusivity in the gas by observing the energy flow between the two clouds. [Preview Abstract] |
Thursday, May 31, 2018 8:24AM - 8:36AM |
Q03.00003: Multi-body interactions in few-body arrays of fermionic 87Sr Akihisa Goban, Ross Hutson, G. Edward Marti, Sara Campbell, Michael Perlin, Jose D'Incao, Paul Julienne, Ana-Maria Rey, Jun Ye Ultracold Alkaline-earth (AE) atoms provide unique platforms for advancing atomic clocks, quantum information processing, and quantum simulation. There is particular interest in the use of fermionic AE(-like) atoms to perform quantum simulations of large-spin quantum magnetism, the Kondo effect, and high-energy lattice gauge theories. Multi-body interactions, which cannot be broken down into sums of pairwise interactions, hold the potential to create even more exotic states of quantum matter, but they are yet to be explored in fermionic AE atoms. Here, we use clock spectroscopy of ${}^{87}$Sr to isolate arrays of few-body systems in a three-dimensional optical lattice and directly observe the onset of $SU(10)$-symmetric multi-body interactions in AE fermions. We observe effective three-body interactions in density-dependent shifts of the spectroscopic signal that are non-linear in the occupation number of the few-body system. We additionally measure three-body recombination rates as a function of particle density and occupation-number. Supported by the theory, these measurements suggest favorable energy and timescales of the interactions for their use in a ultracold atom quantum simulator. [Preview Abstract] |
Thursday, May 31, 2018 8:36AM - 8:48AM |
Q03.00004: Contact and sum-rules in a homogeneous Fermi gas at unitarity Christopher Vale, Cecile Carcy, Sascha Hoinka, Marcus Lingham, Paul Dyke, Carlos Kuhn, Hui Hu We present an experimental study of the high-energy excitations in a near-homogenous unitary Fermi gas. Using focussed beam Bragg spectroscopy, we measure the dynamic structure factor in the centre of a harmonically trapped cloud, where the density varies by less than ten percent. By employing sum-rules, we map the evolution of Tan's universal contact parameter across the superfluid to normal fluid transition. For Bragg frequencies higher than approximately twice the atomic recoil frequency, the dynamic structure factor approaches the limiting behavior predicted by theory. We also use the kinetic (second-moment) sum-rule to determine the internal energy at unitarity which is very sensitive to the high frequency tail. [Preview Abstract] |
Thursday, May 31, 2018 8:48AM - 9:00AM |
Q03.00005: A Fermi Degenerate Gas of Ground State Polar Molecules Luigi De Marco, Giacomo Valtolina, Kyle Matsuda, William Tobias, Jacob Covey, Jun Ye Ultracold polar molecules provide unheralded opportunities for exploring many-body physics and especially for emulating spin systems that go beyond nearest-neighbor interactions. In particular, owing to the large molecular electric dipole moment, the long-range dipole-dipole force allows us to investigate phenomena where the complex interplay between disorder and interaction strength dominates the system's dynamics and gives rise to novel quantum phases. While low-entropy samples have been produced in a 3D lattice, in this talk, I will present our recent progress towards generating a deeply degenerate gas of polar KRb molecules in two dimensions. In the new generation KRb apparatus at JILA, we have produced in excess of 40,000 ground state molecules in DC electric fields up to 10~kV/cm. By combining such fields with strong optical confinement, we not only stabilize the molecules against chemical reactions, but can also explore efficient evaporative cooling in a 2D configuration. This provides us with a clear path forward to producing a bulk Fermi degenerate gas of polar molecules. [Preview Abstract] |
Thursday, May 31, 2018 9:00AM - 9:12AM |
Q03.00006: Observation of strongly interacting Fermi gases and orbital Feshbach molecules of Ytterbium atoms Giacomo Cappellini, Lorenzo Livi, Lorenzo Franchi, Massimo Inguscio, Jacopo Catani, Leonardo Fallani The existence of long-lived electronic states is a remarkable property of two-electron atoms such as Ytterbium. These states can be addressed and manipulated with ultranarrow lasers, allowing for the investigation of new phenomena in which multiple degrees of freedom are involved as well as for the realization of new quantum simulation and information schemes. I will report on the experimental realization of a strongly interacting ultracold Fermi gas of $^{173}$Yb atoms in different electronic states obtained by exploiting a novel kind of Feshbach resonance, the recently proposed Orbital Feshbach resonance, based on the orbital spin-exchange mechanism between atoms in different electronic and nuclear spin states. I will also report on the observation and characterization of orbital molecules formed by two Yb atoms in different electronic states on the repulsive side of the resonance, a first step towards the investigation of the BEC-BCS crossover in fermionic systems with multiple degrees of freedom. [Preview Abstract] |
Thursday, May 31, 2018 9:12AM - 9:24AM |
Q03.00007: Investigation of low-outgassing lithium sources for a portable cold-atom vacuum standard Eric Norrgard, Daniel Barker, James Fedchak, Nikolai Klimov, Julia Scherschligt, Stephen Eckel The aim of the Cold Core Technology Platform at NIST is to produce chip-scale sensors and standards based on cold atoms, including a device based on trapped cold atoms which is simultaneously a primary standard and an absolute sensor of vacuum. Translating these cold atom-based technologies into deployable sensors requires an atomic source which is scaleable, lightweight, and suitable for ultra-high vacuum. We present two potential atom sources for such applications. One, an alkali metal dispenser made from 3D-printed titanium, loads a Li magneto-optical trap (MOT) of 10\textasciicircum 7 atoms with a low outgassing rate. In a second application, atoms are loaded into a MOT by light-induced atomic desorption (LIAD) from the surface of a vacuum viewport. A MOT of roughly 10\textasciicircum 4 atoms was loaded in this manner while increasing the pressure in the vacuum chamber by less than 50{\%}, or 2x10\textasciicircum -10 torr. To our knowledge, this is the first observation of LIAD of Li. [Preview Abstract] |
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