Effect of crystal damage on superconductivity in the transition-metal layer compounds

The superconducting properties of the transition-metal dichalcogenides TaS2, TaSe2, NbS2, and NbSe2 have been studied as a function of structural disorder induced by heavy-ion bombardment and by deintercalation at temperatures between 300 and 800 K. Changes in Tc similar to those seen on intercalation by metal ions and organic molecules were observed but there was no increase in the anisotropy of the critical magnetic fields. The changes in Tc are attributed to changes in the electronic structure at the respective Fermi surfaces beyond previously considered changes in the density of states at the Fermi surface on intercalation. © 1975 The American Physical Society.