Free-fermionic Schur Functions

We use the free-fermionic six-vertex model to define the double factorial (supersymmetric) Schur functions which generalize the Schur functions, the factorial Schur functions, the double Schur functions, the supersymmetric Schur functions, the factorial supersymmetric Schur functions, and other less-known relatives of Schur functions. We show how to use the techniques of the lattice model to give intuitive proofs for Cauchy identity, Jacobi-Trudi Identity, Factorization, Determinant expression, and other familiar results.