Phase coherence in the inelastic cotunneling regime
  Two quantum dots with tunable mutual tunnel coupling have been embedded in a two-terminal Aharonov-Bohm geometry. Aharonov-Bohm oscillations are investigated in the cotunneling regime. Visibilities of more than 0.8 are measured indicating that phase-coherent processes are involved in the elastic and inelastic cotunneling. An oscillation-phase change of pi is detected as a function of bias voltage at the inelastic cotunneling onset. 
M. Sigrist, T. Ihn, K. Ensslin, D. Loss, M. Reinwald, and W.   Wegscheider