Implications of a light stop for the spontaneous CP breaking at finite   temperature in a nonminimal supersymmetric standard model
  We study the implications of a light stop for the spontaneous CP breaking at finite temperature in the Higgs sector of the Minimal Supersymmetric Standard Model with a gauge singlet. Assuming CP conservation at zero temperature, we show that the presence of a large mixing between the left- and the right-handed stops can trigger easily the spontaneous breaking of CP inside the bubbles nucleated during the electroweak phase transition. This allows to avoid the fine-tuning among the vacuum expectation values in the region of interest for the generation of the baryon asymmetry, namely the bubble walls, which has been recently analized. 
D. Comelli, M. Pietroni and A. Riotto