Periodic ground state for the charged massive Schwinger model
  It is shown that the charged massive Schwinger model supports a periodic vacuum structure for arbitrary charge density, similar to the common crystalline layout known in solid state physics. The dynamical origin of the inhomogeneity is identified in the framework of the bozonized model and in terms of the original fermionic variables. 
S. Nagy, J. Polonyi, and K. Sailer