  We show that a generalized charge SU(2) symmetry of the one-dimensional (1D)
Hubbard model in an infinitesimal flux $\phi$ generates half-filling states
from metallic states which lead to a finite charge stiffness $D(T)$ at finite
temperature $T$, whose $T$ dependence we study. Our results are of general
nature for many integrable quantum lattice systems, reveal the microscopic
mechanisms behind their exotic $T>0$ transport properties and the interplay
with T=0 quantum-phase transitions, and contribute to the further understanding
of the transport of charge in systems of interacting ultracold fermionic atoms
in 1D optical lattices, quasi-1D compounds, and 1D nanostructures.
