  The recent discovery of superconductivity at moderately high temperature (26
K to 55 K) in doped iron-based pnictides (LnO_{1-x}F_xFeAs, where Ln = La, Ce,
Sm, Pr, Nd, etc.), having layered-structure-like cuprates, has triggered
renewed challenge towards understanding the pairing mechanism.
  After reviewing the current findings on these systems, a theoretical model of
a combined mechanism is suggested in which the phonon-mediated and
distortion-field-mediated pairing processes give the right order of
superconducting critical temperature T_c. The distortion-field modes arise from
Jahn-Teller or pseudo Jahn-Teller effects due to degenerate or near-degenerate
iron 3d_{xz} and 3d_{yz} orbitals.
