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 contribute a large effect at high temperatures. The two key differences between optical-and acoustic-phonon-mediated drag are (i) the optical-phonon-mediated interlayer interaction is short-ranged due to the negligible group velocity at the Brillouin zone center, and (ii) 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. [S0163-1829(98)05219-9]
