Using the technique of phonon-drag imaging on two-dimensional electron
gases (2DEGs), we have observed novel patterns, which cannot be direc
tly explained using the simple theory of phonon focusing that has prev
iously been applied to such images. In order to explain these new resu
lts, a theory has been developed in which the phonon-drag effect is de
scribed as a point charge dipole, and the response is calculated inclu
ding the full detector geometry. This removes the previous invalid ass
umption that the 2DEG acts as a point detector. Our results show that
the whole sample geometry, including the contacts, strongly contribute
s to the phonon-drag signal, and that the effects seen in the experime
nts can only be accurately reproduced when this is taken into account.
Thus our model provides the first accurate description of the phonon-
drag imaging experiments. Comparison of the simulated images, which ta
ke into account the finite detector geometry, with the experimentally
obtained images for different sample geometries shows excellent agreem
ent, indicating the success of the model in accurately describing the
experimental system.