Department of Physics, Engineering Physics & Astronomy

Queen's University
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Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

Spin Transport in a Unitary Fermi Gas

Joseph Thwissen
University of Toronto

Thurs., April 3, 2014
10:30 AM @ Stirling Hall 401

Abstract:

In the unitary limit, s-wave scattering between particles is as strong as quantum mechanics allows. The thermodynamic properties of unitary Fermi gases are called "universal", since they do not depend on the strength or physical origin of their interactions. For the same reason, one might expect unitary dynamics to be universal. Recent measurements test this hypothesis, by measuring transport properties such as shear viscosity and spin diffusivity. In the case of shear viscosity, similar viscosity-to-density ratios are measured in ultra cold gas experiments and in the quark-gluon plasma. Those experiment are compared to a hydrodynamics calculation using the conjectured AdS/CFT duality.

In our work, we study the dynamics of a transversely magnetized unitary Fermi gas in an inhomogeneous magnetic field. We find that demagnetization dynamics are driven by diffusive spin transport with a diffusion constant that saturates at low temperatures to the conjectured quantum-mechanical lower bound, roughly hbar/m, where m is the particle mass. The development of pair correlations is observed by measuring Tan's contact parameter.