Sauter-Schwinger like tunneling in tilted Bose-Hubbard lattices in the   Mott phase
  We study the Mott phase of the Bose-Hubbard model on a tilted lattice. On the (Gutzwiller) mean-field level, the tilt has no effect -- but quantum fluctuations entail particle-hole pair creation via tunneling. For small potential gradients (long-wavelength limit), we derive a quantitative analogy to the Sauter-Schwinger effect, i.e., electron-positron pair creation out of the vacuum by an electric field. For large tilts, we obtain resonant tunneling related to Bloch oscillations. 
Friedemann Queisser, Patrick Navez, and Ralf Sch\"utzhold
quant-ph cond-mat.quant-gas