Photoemission and inverse resonant photoemission studies of ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{Ca}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{10+\mathit{y}}$

We present photoemission and inverse photoemission results for single and polycrystalline ${\mathrm{Tl}}_2$ ${\mathrm{Ba}}_{2\mathrm{-}\mathrm{x}}$ ${\mathrm{Ca}}_{2+\mathrm{x}}$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{10+\mathit{y}}$. Studies of the occupied states reveal Cu-O and Tl 6s hybrid states within ∼8 eV of the Fermi level $E_F$. Tl 4f emission characteristic of a single chemical environment, the Cu 2$p_{3/2}$ main line and satellites, complex O 1s emission derived from chemically inequivalent oxygen sites, and Ca and Ba emission reflecting Ca-Ba disorder within the unit cell were observed. Inverse-photoemission results show a low density of states within ∼1 eV of $E_F$ and structure at ∼3, ∼7, 9.6, and 14 eV above $E_F$ that is associated with Tl 6p, Ba 5d, Ca 3d, and Ba 4f empty levels. Resonant inverse-photoemission highlights the O 2p holes near $E_F$. Differences and similarities to ${\mathrm{Bi}}_2$ ${\mathrm{Ca}}_{1+\mathrm{x}}$ ${\mathrm{Sr}}_{2\mathrm{-}\mathrm{x}}$ ${\mathrm{Cu}}_2$ ${\mathrm{O}}_{8+\mathit{y}}$ are discusse