Correlations and fluctuations in Heisenberg spin chains


J.S. Caux

Institute for Theoretical Physics, University of Amsterdam


The Heisenberg spin-1/2 chain is one of the most famous
paradigms for quantum critical behaviour, which occurs when
quantum fluctuations are sufficiently strong to induce
criticality as a parameter such as doping or magnetic field
is varied.  In this spirit, and motivated by recent experiments on
quasi-one-dimensional antiferromagnets in a magnetic field (including
inelastic neutron scattering studies), we consider the general case
of an anisotropic Heisenberg magnet in a transverse external field.
We propose a general method for the computation of ground-state
and thermodynamical properties, and dynamical correlation functions.
Comparisons with numerical DMRG results and experimental data
will be presented.