Pressure-induced effects in high-T-c superconductors: Raman scattering as a probe of charge-lattice dynamics under high pressure

摘要

The Raman spectra of Bi2Sr2CaCu2O8+d (Bi2212) and YBa2Cu4O8 (Y124) have been investigated as a function of hydrostatic pressure. In both the overdoped Bi2212 and the underdoped Y124, the 140 cm(-1) Cu mode exhibits a pronounced nonlinear pressure dependence which correlates to the dependence of T-c versus pressure. We argue that this behavior is a signature of charge-redistribution effects induced by compression. For Bi2212, we also find that the mode-specific Gruneisen parameters scale inversely with the corresponding phonon frequencies, a behavior which is reminiscent of phonon pressure dependences in molecular solids. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 12]