Fermi Gases in Bichromatic Superlattices
Designer materials made of ultra-cold atoms and light provide
new paradigms for emulating exotic layered systems. Bichromatic superlattices, comprising standing waves at two optical wavelengths,
enable control and study of both dimensionality and dispersion in layered,
strongly correlated Fermi gases, offering new opportunities in the search
high-temperature superconductors and superfluids.
Most layered materials are quasi-two-dimensional, neither
two-dimensional, like a sheet, nor three-dimensional, like a gas, but somewhere
in between. In quasi-2D layers with an unequal number of spin-up and spin-down
electrons, particularly strong attraction between pairs of electrons with
opposite spins is predicted to achieve the highest possible superconducting
transition temperatures, needed for practical super-efficient power
transmission. To understand these
materials, we emulate them with a layered, ultra-cold Fermi gas of atoms, where
precise control of the attraction, spin-composition, dimensionality and
dispersion provides new tests of theory.
The proposed program examines the properties of mesoscopic
Fermi gas layers, containing several hundred atoms each, which are created by
combining the tunable periodic potential of a bichromatic superlattice along
one axis, with the smooth potential of a CO2 laser trap that
provides tunable confinement along the orthogonal (transverse) axes. The data
obtained using this non-perturbative many-body system will enable precise
feedback between theory, computation and experiment, to test state-of-the-art
calculational methods, which are an important focus of the DOE theory program.
Experiments employing this new trapping system will be used
to address two important scientific goals: 1) Elucidation of the effects of
dimensionality and confining potential shape on the enhancement of
high-temperature superfluidity in a layered, strongly correlated Fermi gases;
2) Control of dispersion and the study of tunable Dirac points in one
dimension, where the cloud behaves as a relativistic gas.