The dynamics of integer quantum Hall edge states far from equilibrium

Interference effects involving electrons in vacuum have played an
important part in the development of quantum physics, from the
observation of electron diffraction by Davison and Germer in 1927 to
the demonstration of the Aharonov-Bohm effect by Chambers in 1960.
Interference effects involving electrons in solids take a central
place in some areas of condensed matter physics, but are generally
more delicate to observe than in vacuum, because they may be obscured
by scattering from impurities, phonons or other electrons. Quantum
Hall edge states provide an exception to this general rule, being
almost ideal waveguides for electrons in a semiconductor. The
properties of quantum Hall edge states have been investigated in a
series of experiments of increasing sophistication over the past two
decades.  In particular, recent experiments probe coherence and
many-body dynamics far from thermal equilibrium. I will review some of
these experiments and describe the theoretical ideas which have been
developed to understand them.