Quantum-limited spin transport

We have observed quantum-limited spin transport in strongly interacting two-dimensional Fermi gases. We measure the rate of demagnetization of polarized samples in the presence of a magnetic field gradient, which drives coherence-eroding spin currents. We found that a lower bound on spin diffusivity, of roughly hbar/m, is respected for all interaction strengths, temperatures, and applied gradients accessible in our setup. 

Luciuk et al., Physical Review Letters, 118, 130405 (2017)
[doi: 10.1103/PhysRevLett.118.130405] [journal link]

Fluorescence microscopy of individual atoms in an optical lattice

We demonstrate fluorescence microscopy of individual fermionic potassium atoms in a 527-nm-period optical lattice. Using electromagnetically induced transparency (EIT) cooling on the 770.1-nm D1 transition of 40K, we find that atoms remain at individual sites of a 0.3-mK-deep lattice, with a 1/e pinning lifetime of 67(9)s, while scattering ~1000 photons per second. The plane to be imaged is isolated using microwave spectroscopy in a magnetic field gradient, and can be chosen at any depth within the three-dimensional lattice. With a similar protocol, we also demonstrate patterned selection within a single lattice plane. High resolution images are acquired using a microscope objective with 0.8 numerical aperture, from which we determine the occupation of lattice sites in the imaging plane with 94(2)% fidelity per atom. Imaging with single-atom sensitivity and addressing with single-site accuracy are key steps towards the search for unconventional superfluidity of fermions in optical lattices, the initialization and characterization of transport and non-equilibrium dynamics, and the observation of magnetic domains. 

Edge et al., Physical Review A 92, 063406 (2015) as ''Editors' Suggestion''
[doi: 10.1103/PhysRevA.92.063406][journal link]

observation of p-wave contacts

Observation of two new physical quantities, the p-wave contacts, via time-resolved spectroscopy. We study how correlations in our system develop after "quenching" the atoms into a state with near resonant p-wave interactions. The contacts appear as a unique frequency scaling in the spectra. These observations suggest a new way to characterize any gas with short-ranged p-wave interactions. 

Luciuk et al., Nat. Phys. (2016)
Yu et al., PRL 115, 135304 (2015)

Observation of the Leggett-Rice Effect in a unitary Fermi Gas

Our paper on spin transport in a strongly interacting Fermi gas investigates how transverse spin currents are twisted by the spins that are responsible for their generation (a). We measure the Leggett-Rice parameter gamma that characterizes this precession (b), as well as the transverse spin diffusivity (c), as a function of temperature and interaction parameter kFa. 

Trotzky et al., PRL 114, 015301 (2015)

Planckian transport bound in spin diffusivity

Spin Transport at the Planck Limit in a unitary Fermi gas. Using a spin echo, we measure the transverse demagnetization dynamics of a Fermi gas at a scattering resonance. We find that the magnetization dynamics are diffusive, described with a transverse spin diffusion constant Ds, whose value saturates to hbar/m at low tempeature.

Bardon et al., Science 344, 722 (2014)

Quantum transport across a barrier

The frequency with which an ultracold rubidium superfluid oscillates between the two sides of a barrier, as a function of barrier height. The white dots are measured frequencies, and the black lines are ab-initio theory calculations. JM is the two-mode Josephson Model, HD is a hydrodynamic model, and GPE is the Gross Pitaevskii equation. The barrier height is shown divided by the chemical potential of the condensate.

LeBlanc et al, PRL 106, 025302 (2011)

a degenerate Fermi gas

The pictures above are absorption images of Potassium 40 atoms at several temperatures. As the temperature is reduced, fermions occupy lower and lower energy levels in the trap, and the cloud sized is reduced. However, at temperatures below the Fermi temperature, lower energy states are completely occupied, and eventually filled up to the Fermi energy (indicted by the red circle above). This quantum degenerate state was acheived by sympathetic cooling in the microfabricated magnetic trap using a reservoir of Rubidium 87 atoms 

August 2005

Bose-Einstein condensation

Images of a cloud of Rubidium 87 atoms above and below the Bose-Einstein phase transition. left: 120,000 thermal atoms at 960nK; center: 70,000 atoms at 360nK, just below Tc; right: a nearly pure Bose-Einstein condensate of 45,000 atoms. Images are roughly 1mm by 1mm, and taken after 10ms of free expansion. Height in these plots corresponds to observed atomic density. 

April 2005

first MOT!

Image of our first magneto optical trap! Long live the lab!

December 2003