News

Sat January 1, 2011

Feynman diagrams versus Feynman quantum emulator

Precise understanding of strongly interacting fermions, from electrons in modern materials to nuclear matter, presents a major goal in modern physics. However, the theoretical description of interacting Fermi systems is usually plagued by the intricate quantum statistics at play. Here we present a cross-validation between a new theoretical approach, Bold Diagrammatic Monte Carlo (BDMC), and...
News type:
Sat January 1, 2011

Revealing the Superfluid Lambda Transition in the Unviersal Thermodynamics of a Unitary Fermi Gas

Fermi gases, collections of fermions such as neutrons and electrons, are found throughout nature, from solids to neutron stars. Interacting Fermi gases can form a superfluid or, for charged fermions, a superconductor. We have directly observed the superfluid phase transition in a strongly interacting Fermi gas via high-precision measurements of the local compressibility, density and...
News type:
Sat January 1, 2011

Evolution of Fermion Pairing from Three to Two Dimensions

Interacting fermions in coupled two-dimensional (2D) layers present unique physical phenomena and are central to the description of unconventional superconductivity in high-transition-temperature cuprates and layered organic conductors. Reduced dimensionality enhances the effect of fluctuations, while interlayer coupling can stabilize superconductivity and even amplify the transition temperature. A fermionic superfluid loaded into a periodic potential should...
News type:
Sat January 1, 2011

Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas

Spin fluctuations and density fluctuations are studied for a two-component gas of strongly interacting fermions along the BEC-BCS crossover [1].  Spin fluctuations are observed by directly measuring the difference in densities for the two spin states.  This was done by using a probe laser which had equal detuning from both states, but with opposite signs.
News type:
Sat January 1, 2011

A cryogenic beam of refractory, chemically reactive molecules with expansion cooling

Atomic and molecular beams have been valuable tools for precision measurement of atomic and molecular spectra for the past several decades.  In order to achieve good signal to noise in a beam spectroscopy experiment, it is important to have high fluxes, low forward velocity (to increase interaction time), and, in the case of molecules, cold...
News type:
Sat January 1, 2011

A Cold and Slow Molecular Beam

Due to the rich internal structures and the long range, anisotropic, and tunable interaction of polar molecules, increasingly efforts have been devoted to producing cold polar molecules for studying quantum simulation, cold, controlled chemistry, and precision measurements. We reported producing a cold, slow calcium monohydride molecular beam using a two-stage cryogenic buffer gas cell. This...
News type:
Sat January 1, 2011

Quantum degenerate Bose-Fermi mixture of chemically different atomic species with widely tunable interactions

We have created a quantum degenerate Bose-Fermi mixture of 23Na and 40K with widely tunable interactions via broad interspecies Feshbach resonances. Twenty Feshbach resonances between 23Na and 40K were identified. The large and negative triplet background scattering length between 23Na and 40K causes a sharp enhancement of the fermion density in the presence of a...
News type: