Incollection,
Quantum criticality beyond the Landau-Ginzburg-Wilson paradigm
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Abstract
The theory of second order phase transitions is one of
the foundations
of modern statistical mechanics and condensed matter theory. A
central concept
is the observable 'order parameter', whose non-zero average value
characterizes one or more phases and usually breaks a symmetry of the
Hamiltonian. At large distances and long times, fluctuations of the
order
parameter(s) are described by a continuum field theory, and these
dominate the
physics near such phase transitions. This talk will show that near
second order
quantum phase transitions, subtle quantum interference effects can
invalidate
this paradigm. A theory of quantum critical points in a variety of
experimentally relevant two-dimensional antiferromagnets will be
presented. The
critical points separate phases characterized by conventional 'confining'
order parameters. Nevertheless, the critical theory is naturally
expressed in
terms of new emergent, 'deconfined' degrees of freedom associated with
fractionalization of the order parameters, along with an emergent
gauge field.
This new paradigm for quantum criticality may be the key to
resolving a number
of experimental puzzles in correlated electron systems.
