  We consider a quantum Hall system with an antidot acting as an energy
dependent scatterer. In the purely charge case, we find deviations from the
Wiedemann-Franz law that take place in the nonlinear regime of transport. We
also discuss Peltier effects beyond linear response and describe both effects
using magnetic-field asymmetric transport coefficients. For the spin case such
as that arising along the helical edge states of a two-dimensional topological
insulator, we investigate the generation of spin currents as a result of
applied voltage and temperature differences in samples attached to
ferromagnetic leads. We find that in the parallel configuration the spin
current can be tuned with the leads' polarization even in the linear regime of
transport. In contrast, for antiparallel magnetizations the spin currents has a
strict nonlinear dependence on the applied fields.
