Phonon-drag thermopower of a two-dimensional electron gas in a quantizing magnetic field

A formula is developed which gives the phonon drag thermopower $S_g$ of a two-dimensional (2D) electron gas coupled to 3D acoustic phonons in a quantizing magnetic field. Evaluation of the formula with realistic parameter values for a GaAs-${\mathrm{Ga}}_{\mathrm{x}}$ ${\mathrm{Al}}_{1\mathrm{-}\mathrm{x}}$As heterojunction in a field of 15 T yields a maximum value of 16.4 ${\mathrm{mVK}}^{\mathrm{-}1}$ at 6 K in excellent agreement with experimental data [for sample 1 of Fletcher et al., Phys. Rev. B 33, 7122 (1986)].