Thermofield Quantum Electrodynamics in 1 + 1 Dimensions at Finite   Chemical Potential: A Bosonization Approach
  The recent generalization of the Lowenstein-Swieca operator solution of Quantum Electrodynamics in 1+1 dimensions to finite temperature in Thermofield Dynamics is further generalized to include a non-vanishing chemical potential. The operator solution to the Euler-Lagrange equations respecting the Kubo-Martin-Schwinger condition is constructed. Two forms of this condition and their associated solutions are discussed. The correlation functions of an arbitrary number of chiral densities are computed in the thermal theta-vacuum. 
R. L. P. G. Amaral, L. V. Belvedere and K. D. Rothe
hep-th