On the existence of negative energy states in QED in the temporal gauge
  It is generally assumed that the vacuum state is the quantum state with the lowest energy. However, it has been shown that this is not the case for a Dirac-Maxwell field in the temporal gauge. In this paper we will present another proof, different from that presented in previous work, which shows that the vacuum state is not the minimum energy state for a Dirac-Maxwell field in the temporal gauge. 
Dan Solomon