Surface study of the 83-K superconductor ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ by low-energy electron diffraction and angle-resolved inverse photoemission spectroscopy

Low-energy-electron-diffraction (LEED) and angle-resolved inverse photoemission spectroscopy (ARIPES) have been applied to the cleaved surface of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$ single crystals. The LEED pattern shows a surface lattice which is identical to the superlattice found in the bulk structure. ARIPES along the ΓX($a^{\mathrm{*}}$) direction yields nondispersive unoccupied electronic states at 2.9 and ∼5 eV above the Fermi energy attributed to Bi-O derived conduction bands. At 0.47 ΓX the experimental density of states at the Fermi level increases. This may be due to the crossing of the O(1) band through $E_F$ derived from oxygen atoms in the Cu-O planes.