Probing many-body physics with cold atoms: The Higgs boson and quantum
hexatic order
Georg Bruun
Aarhus University
Tuesday, 10 June 2014, 14:30
Matfys library
Abstract:
In this talk, I describe how cold atoms can be used to test two phenomena
which play a key role in our description of quantum many-body physics.
The first is the Higgs mode, which plays a fundamental role for our
understanding of both low and high energy physics, giving elementary
particles their mass and leading to collective modes in condensed matter
and nuclear systems. The Higgs mode has been observed in a limited number
of table-top systems, where it however is characterised by a short
lifetime due to decay into a continuum of modes. A major goal which has
remained elusive so far, is therefore to realise a long-lived Higgs mode
in a controllable system. Here, we show how an undamped Higgs mode can be
observed unambiguously in a Fermi gas in a two-dimensional trap, close to
a quantum phase transition between a normal and a superfluid phase. The
second phenomena is the hexatic phase, which is a phase in between a
liquid and a crystal. We show how such a phase can be realised in the
quantum regime for the first time, using a two-dimensional gas of dipolar
molecules. We derive approximate phase diagrams using a pair of Lindemann
criteria, suitably adapted to deal with effects of thermal fluctuations in
two dimensions. The hexatic phase is predicted to survive down to very
low temperatures.