Influence of incommensurate structure on the elastic constants of crystalline Bi2Sr2CaCu2O8+δ by Brillouin light scattering spectroscopy

Abstract

Brillouin light scattering spectroscopy was used to probe the room-temperature elasticity of crystalline high- T _c superconductor Bi _2 Sr _2 CaCu _2 O _8+ _δ . A complete set of best-estimate elastic constants was obtained using established relationships between acoustic phonon velocities and elastic constants along with a simple expression relating crystal elastic constant C _22 to the corresponding constants of the constituent incommensurate sublattices. This latter relationship, which was derived and validated in the present work, has important implications for those studying incommensurate systems as it appears that it may be applied in its general form to any composite incommensurate crystal. The results obtained in this work are also consistent with sublattice assignments of Bi _2 Sr _2 O _4 and CaCu _2 O _4 reported in a previous Brillouin scattering study.

Keywords

• Bi-2212
• brillouin light scattering
• elastic constants
• incommensurate structure
• acoustic phonons
• cuprates