Lecture 20. Order parameter and natural history of phases
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چکیده
Why do we need an order parameter at all? We need it to distinguish different bulk phases, or more precisely, to characterize distinct features of equilibrium properties of different bulk phases. Although scattering experiments tell us microscopic distinctions of various phases, it is important to recognize that different phases are distinguishable macroscopically through macroscopic quantities. That is, we have only to have a thermodynamic variable that can distinguish phases. Roughly speaking, an order parameter describing a phase transition between two phases is a thermodynamic quantity that is zero in one phase and non-zero in the other.
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