Metal-insulator transition in ${\mathrm{C}}_{60}$ polymers

Variations in the band structures of ${\mathrm{C}}_{60}$ polymers are studied, when π-conjugation conditions are changed. We discuss a metal-insulator transition, using a semiempirical model with the Su-Schrieffer-Heeger-type electron-phonon interactions. We find that electronic structures change among direct-gap insulators and the metal, depending on the degree of π conjugations. High-pressure experiments could observe such pressure-induced metal-insulator transitions. The transition from one insulator to another insulator is reentrant, and is specific to the ${\mathrm{C}}_{60}$-polymer system.