  The one-dimensional Hubbard model is an exceptional integrable spin chain
which is apparently based on a deformation of the Yangian for the superalgebra
gl(2|2). Here we investigate the quantum-deformation of the Hubbard model in
the classical limit. This leads to a novel classical r-matrix of trigonometric
kind. We derive the corresponding one-parameter family of Lie bialgebras as a
deformation of the affine gl(2|2) Kac-Moody superalgebra. In particular, we
discuss the affine extension as well as discrete symmetries, and we scan for
simpler limiting cases, such as the rational r-matrix for the undeformed
Hubbard model.
