QUANTITATIVE MODEL OF PHONON-DRAG IMAGING EXPERIMENTS

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.