Anomalous band folding due to the BiO superstructure in Bi2Sr2CaCu2O8 studied by angle-resolved photoemission.

Abstract

Angle-resolved photoemission measurement has been performed on a twin-free ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ single crystal to study the band-folding effect due to the BiO superstructure. It was found that the superstructure running along the b axis considerably modulates the electronic structure near the Fermi level (${\mathit{E}}_{\mathit{F}}$) in that direction, almost smearing out the dispersive feature of a band which crosses the Fermi level. In contrast with the energy region near ${\mathit{E}}_{\mathit{F}}$, the main body of the valence band (1 to 7 eV in binding energy) shows a comparable but different energy dispersion between the a- and b-axis directions. This indicates that the band-folding effect may be different between the near-${\mathit{E}}_{\mathit{F}}$ region and the whole valence band in ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$.