In this question: https://mathoverflow.net/questions/272306/what-techniques-are-there-to-prove-schur-positivity, one of the techniques listed to prove Schur-positivity is called a Type-A crystal proof, which apparently Stembridge characterized. Does anyone have a link to the relevant Stembridge paper, or to something that can explain this in more detail?
I suppose that it is A local characterization of simply-laced crystals (Trans. Am. Math. Soc. 355, No. 12, 4807-4823 (2003)).