  The statistical model of crystal melting represents BPS configurations of
D-branes on a toric Calabi-Yau three-fold. Recently it has been noticed that an
infinite-dimensional algebra, the quiver Yangian, acts consistently on the
crystal-melting configurations. We physically derive the algebra and its action
on the BPS states, starting with the effective supersymmetric quiver quantum
mechanics on the D-brane worldvolume. This leads to remarkable combinatorial
identities involving equivariant integrations on the moduli space of the
quantum mechanics, which can be checked by numerical computations.
