There Is No Efimov Effect for Four or More Particles
Ralph D. Amado, Frederick C. Greenwood · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 1973
We show that the existence of a zero-energy ($n\ensuremath{-}1$)-body bound state will not produce an infinite number of $n$-body bound states for $n\ensuremath{\ge}4$. We show this in particular for $n=4$, and sketch the proof for $n>4$.