  We investigate nonlinear thermoelectric transport through quantum impurity
systems with strong on-site interactions. We show that the steady-state
transport through interacting quantum impurities in contact with electron
reservoirs at significantly different temperatures can be captured by an
effective-equilibrium density matrix, expressed compactly in terms of the
Lippmann-Schwinger operators of the system. In addition, the reservoirs can be
maintained at arbitrary chemical potentials. The interplay between the
temperature gradient and bias voltage gives rise to a non-trivial breaking of
particle-hole symmetry in the strongly correlated regime, manifest in the
Abrikosov-Suhl localized electron resonance. This purely many-body effect,
which is in agreement with experimental results, is beyond the purview of
mean-field arguments.
