Friday AMO Journal Club
Regular meetings are held for people interested in atomic, molecular, and optical (AMO) physics each Friday – currently on Zoom from 12noon–1pm. Students and faculty interested in cold atom physics or related topics are welcome to attend. We review and discuss papers from the AMO literature.
Please subscribe to the Physastro_AMO_journal_club mailing list to get announcements, or contact Michael Forbes or Peter Engles for more information.

21 February 2019: Local spin manipulation of quantized atomic currents
For Thursday 21 February 2019 we will discuss:
Spin is a fundamental quantum property of matter, and lifting its degeneracy lies at the heart of subtle transport phenomena and future schemes for quantum information processing. Here, we implement a microscopic spin filter for cold fermionic atoms in a quantum point contact (QPC) which allows us to create fully spinpolarized currents while retaining conductance quantization. Key to our scheme is a nearresonant optical tweezer which induces an effective Zeeman shift inside the QPC while … » More …

31 January 2019: Transient supersolid properties in an array of dipolar quantum droplets
For Thursday 31 January 2019 we will discuss:
We study theoretically and experimentally the emergence of supersolid properties in a dipolar BoseEinstein condensate. The theory reveals a ground state phase diagram with three distinct regimes – a regular BoseEinstein condensate, incoherent and coherent arrays of quantum droplets. In the latter the droplets are connected by a finite superfluid density, which leads – in addition to the periodic density modulation – to a robust phase coherence throughout the whole … » More …

24 January 2019: Rotating Atomic Quantum Gases with LightInduced Azimuthal Gauge Potentials and the Observation of the HessFairbank Effect
For Thursday 24 January 2019 we will discuss:
P.K. Chen, L.R. Liu, M.J. Tsai, N.C. Chiu, Y. Kawaguchi, S.K. Yip, M.S. Chang, and Y.J. Lin
Phys. Rev. Lett. 121, 250401 : Rotating Atomic Quantum Gases with LightInduced Azimuthal Gauge Potentials and the Observation of the HessFairbank EffectWe demonstrate synthetic azimuthal gauge potentials for BoseEinstein condensates from engineering atomlight couplings. The gauge potential is created by adiabatically loading the condensate into the lowest energy Ramandressed state, achieving a coreless vortex state. The azimuthal gauge potentials act as effective rotations and are tunable by the Raman coupling and detuning. We characterize the … » More …

13 December 2018: Density Waves and Jet Emission Asymmetry in Bose Fireworks
For Thursday 13 December 2018 we will discuss:
A Bose condensate subject to a periodic modulation of the twobody interactions was recently observed to emit matterwave jets resembling “fireworks” [Nature 551, 356(2017)]. In this paper, combining experiment with numerical simulation, we demonstrate that these “Bose fireworks” represent a late stage in a complex time evolution of the driven condensate. We identify a “density wave” stage which precedes jet emission and results from interference of matterwaves. … » More …

29 November 2018: Rotating sonic black hole from Spinorbit coupled BoseEinstein condensate
Continuing from last week, for Thursday 29 November 2018 we will discuss:
We show that a sonic analogue of rotating BTZ type of black hole can be realised in a quasitwodimensional spinorbit coupled BEC without any external rotation. The corresponding equation for phase fluctuations in total density mode that describes phonon field in hydrodynamic approximation, is described by a scalar field equation in 2+1 dimension whose spacetime metric can be identified with the spacetime metric of rotating black hole of BTZ type. By time evolving the condensate in a … » More …

15 November 2018: Observation of quantum Hawking radiation and its entanglement in an analogue black hole
Inspired by Bill Unruh’s talk last week, for Thursday 15 November 2018 we will discuss:
We observe spontaneous Hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole in an atomic Bose–Einstein condensate. Correlations are observed between the Hawking particles outside the black hole and the partner particles inside. These correlations indicate an approximately thermal distribution of Hawking radiation. We find that the highenergy pairs are entangled, while the lowenergy pairs are not, within the reasonable assumption that excitations with different frequencies are not correlated. … » More …

9 May 2018: Experimental demonstration of shaken lattice interferometry
For Thursday 9 May 2018 we will discuss:
We experimentally demonstrate a shaken lattice interferometer. Atoms are trapped in the ground Bloch state of a reddetuned optical lattice. Using a closedloop optimization protocol based on the dCRAB algorithm, we phasemodulate (shake) the lattice to transform the atom momentum state. In this way, we implement an atom beamsplitter and build five interferometers of varying interrogation times TI. The sensitivity of shaken lattice interferometry is shown to scale as T2I, consistent with simulation [1]. Finally, we show that we can measure the sign … » More …

26 Apr 2018: Spinorbit coupling induced quantum droplet in ultracold BoseFermi mixtures
For Thursday 26 April 2018 we will discuss:
Quantum droplets have intrigued much attention recently in view of their successful observations in the ultracold homonuclear atoms. In this work, we demonstrate a new mechanism for the formation of quantum droplet in heteronuclear atomic systems, i.e., by applying the synthetic spinorbit coupling(SOC). Take the BoseFermi mixture for example, we show that by imposing a Rashba SOC between the spin states of fermions, the greatly suppressed Fermi pressure can enable the formation of BoseFermi droplets even for very weak bosonfermion attractions, which are … » More …

19 Apr 2018: Anisotropic Critical Velocity of a Dipolar Superfluid
For Thursday 19 April 2018 we will discuss:
M. Wenzel et al: Anisotropic Critical Velocity of a Dipolar Superfluid [arXiv:1804.04552]
We present transport measurements on a dipolar superfluid using a BoseEinstein condensate of 162^Dy with strong magnetic dipoledipole interactions. By moving an attractive laser beam through the condensate we observe an anisotropic critical velocity for the breakdown of dissipationless flow, which, in the spirit of the Landau criterion, can directly be connected to the anisotropy of the underlying dipolar excitation spectrum. In addition, the heating rate above this critical velocity reflects the same anisotropy. Our observations are in excellent agreement with simulations based on … » More …

5 Apr 2018: Shockwaves in the UFG
For Thursday 5 April 2018 we will discuss the following article:
We study the propagation of shock waves in superfluid Fermi gases in the BECBCS crossover. Unlike in other superfluid systems, where shock waves have already been studied and observed, Fermi gases can exhibit a subsonic dispersion relation for which the shock wave pattern appears at the tail of the wavefront. We show that this property can be used to distinguish between a subsonic and a supersonic dispersion relation at … » More …
Headlines
 21 February 2019: Local spin manipulation of quantized atomic currents
 31 January 2019: Transient supersolid properties in an array of dipolar quantum droplets
 24 January 2019: Rotating Atomic Quantum Gases with LightInduced Azimuthal Gauge Potentials and the Observation of the HessFairbank Effect
 13 December 2018: Density Waves and Jet Emission Asymmetry in Bose Fireworks
 29 November 2018: Rotating sonic black hole from Spinorbit coupled BoseEinstein condensate
 15 November 2018: Observation of quantum Hawking radiation and its entanglement in an analogue black hole
 9 May 2018: Experimental demonstration of shaken lattice interferometry
 26 Apr 2018: Spinorbit coupling induced quantum droplet in ultracold BoseFermi mixtures
 19 Apr 2018: Anisotropic Critical Velocity of a Dipolar Superfluid
 5 Apr 2018: Shockwaves in the UFG