  Thermally driven colloidal transport is, to a large extent, due to the
thermoelectric or Seebeck effect of the charged solution.We show that, contrary
to the generally adopted single-particle picture, the transport coefficient
depends on the colloidal concentration. For solutions that are dilute in the
hydrodynamic sense, collective effects may significantly affect the
thermophoretic mobility. Our results provide an explanation for recent
experimental observations on polyelectrolytes and charged particles and suggest
that for charged colloids collective behavior is the rule rather than the
exception.
