Crossover from bad to good metal in BaFe2(As1-xPx)2 induced by isovalent P substitution

Bad metallic behavior or incoherent charge dynamics is characteristic of the normal state of high-transition-temperature copper-oxide superconductors. A parent compound of iron-based superconductors, BaFe2As2, is also a bad metal in the high-temperature phase, whereas its phosphorous counterpart, BaFe2P2, is a good metal. Combined measurements of in-plane resistivity and optical conductivity for BaFe2(As1-xPx)(2) make it possible to disentangle the coherent channel from the incoherent one in the charge transport. The isovalent P substitution promotes coherent motion of carriers without changing the balance of the electron and hole Fermi-surface volume and hence transforms a bad metal into a good metal.