Optical-phonon-induced frictional drag in coupled two-dimensional electron gases

The role of optical-phonons in frictional drag between two adjacent but electrically isolated two-dimensional electron gases is investigated. Since the optical-phonons in III-V materials have a considerably larger coupling to electrons than acoustic phonons (which are the dominant drag mechanism at low T and large separations) it might be expected that the optical phonons will give a large effect high temperatures. The two key differences between optical and acoustic phonon mediated drag are: (1) the optical phonon mediated interlayer interaction is short-ranged due to their negligible group velocity at the Brillouin zone center; and (2) the typical momentum transfer for an optical phonon mediated scattering is relatively large. These considerations make optical phonon mediated drag difficult to see in single subband GaAs systems, but it may be possible to see the effect in double subband GaAs systems or single subband quantum wells in a material with a lower effective mass and lower optical phonon energy such as InSb.