The authors present RPA calculations of the spectra of acoustic plasmons in GaSb, SnTe and Bi. They find that acoustic plasmons only just exist in Bi, having a small critical wavevector of about 10 mu m-1, beyond which they do not exist. In n-GaSb with 1.4*1024 electrons/m3, the calculations give an acoustic plasmon with velocity about 105 ms-1 and relative damping mod omega " mod / omega ' about 0.1. The acoustic plasmon exists for wavevectors up to at least 100 mu m-1 (where the RPA breaks down). In p-SnTe with 1.5*1026 holes/m3, they find an acoustic plasmon with velocity about 2*105 ms-1 and relative damping about 0.1. The spectrum ends abruptly at a critical wavevector which is about 100 mu m-1. They conclude that the prospects for observing acoustic plasmons are poor in Bi, but good in GaSb and SnTe.

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