This paper by Handel and Nobel laureate Charles Kittel, published in the Proceedings of the National Academy of Sciences, investigates the interplay between van der Waals interactions and exciton condensation in semiconductor systems. The work explores how long-range van der Waals forces influence the collective behavior of excitons (bound electron-hole pairs), contributing to understanding of quantum many-body effects and potential Bose-Einstein condensation of excitons in solid-state systems.