Doubly assisted Sauter-Schwinger effect
  We study electron-positron pair creation by a strong and slowly varying electric field, assisted by a weaker and more rapidly changing field (e.g., in the keV regime) plus an additional high-energy (say MeV) photon. It turns out that this combination can yield a pair creation probability which is exponentially larger than in the case where one (or more) of the three ingredients is missing. Apart from a deeper understanding of these non-perturbative phenomena, this double enhancement may pave the way for an experimental verification of this fundamental prediction. 
Greger Torgrimsson, Johannes Oertel, Ralf Sch\"utzhold
hep-th hep-ph quant-ph