Exactly solvable models in QFT

Question

I am looking for references to exactly solvable models in 2-dimensional (lattice or continuum) quantum field theory that exhibit both phases with broken and with unbroken symmetry, so that one can study their phase transition analytically.

Comments

I read the claim that 2D massless Thirring model is exactly solvable. But I don't know if there is a phase transition... you probably know better than me on the subject.

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Massless QFTs are typically conformal field theories and in 2D many of these are exactly solvable in some limited sense, among them Thirring's model - for which all vacuum n-point functions are known. I am specifically interested in the question of phase transition.

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Related threads on PO include

http://www.physicsoverflow.org/16275/what-is-a-good-introduction-to-integrable-models-in-physics?

http://www.physicsoverflow.org/22816/

http://www.physicsoverflow.org/283/

http://www.physicsoverflow.org/206/