future events

Lessons from a high-Tc superfluid: probing local quantities in a strongly interacting Fermi gas

TYPECondensed Matter Seminar
Speaker:Dr. Yoav Sagi
Location:Lidow Nathan Rosen (300)
Abstract:The collective behavior of an ensemble of strongly interacting fermions is
central to many physical systems including liquid 3He, high-Tc
superconductors, quark-gluon plasma, neutron stars, and ultracold Fermi
gases. However, theoretical understanding of strongly interacting fermions
is challenging due to the many-body nature of the problem and the fact
that there is no obvious small parameter for a perturbative analysis.
Ultracold atomic Fermi gases are ideal to shed light on this issue, as
they provide excellent controllability, reproducibility, and unique
detection methods. One of the problems, however, which complicates the
interpretation of these experiments, is the inherent density inhomogeneity
of the gas which arises due to the harmonic confinement. We have developed
a technique to overcome this difficulty by selectively probing atoms near
the center of a trapped gas while still retaining momentum resolution. For
a weakly interacting Fermi gas of 40K atoms, we present measurements of
the momentum distribution that reveal for the first time a sharp Fermi
surface. We then apply the technique to a strongly interacting Fermi gas
at the Feshbach resonance, where we probe the temperature dependence of
the homogeneous Tan’s contact. Finally, we combine the technique with
momentum resolved photoemission spectroscopy to study the outstanding
issue of the nature of the normal state just above the superfluid
transition temperature.