title: Far-infrared absorption and the metal-to-insulator transition in hole-doped cuprates.
abstract: By studying the optical conductivity of Bi(2)Sr(2-x)La(x)CuO(6) and Y(0.97)Ca(0.03)Ba(2)Cu(3)O(6), we show that the metal-to-insulator transition in these hole-doped cuprates is driven by the opening of a small gap at low T in the far infrared. Its width is consistent with the observations of angle-resolved photoemission spectroscopy in other cuprates, along the nodal line of the k space. The gap forms as the Drude term turns into a far-infrared absorption, whose peak frequency can be approximately predicted on the basis of a Mott-like transition. Another band in the midinfrared softens with doping but is less sensitive to the metal-to-insulator transition.
authors.affiliation: CNR-INFM Coherentia and Dipartimento di Fisica, Università di Roma La Sapienza, I-00185 Roma, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Lupi
authors.forename: D
authors.initials: D
authors.lastname: Nicoletti
authors.forename: O
authors.initials: O
authors.lastname: Limaj
authors.forename: L
authors.initials: L
authors.lastname: Baldassarre
authors.forename: M
authors.initials: M
authors.lastname: Ortolani
authors.forename: S
authors.initials: S
authors.lastname: Ono
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ando
authors.forename: P
authors.initials: P
authors.lastname: Calvani