Direct observation of bulk charge modulations in optimally dopedBi1.5Pb0.6Sr1.54CaCu2O8+δ
M. Hashimoto, G. Ghiringhelli, W.-S. Lee, G. Dellea, A. Amorese, C. Mazzoli, K. Kummer, N. B. Brookes, B. Moritz, Y. Yoshida, H. Eisaki, Z. Hussain
Physical Review B
Bulk charge density modulations, recently observed in high critical-temperature (T_c) cuprate superconductors, coexist with the so-called pseudogap and compete with superconductivity. However, its direct observation has been limited to a narrow doping region in the underdoped regime. Using energy-resolved resonant x-ray scattering we have found evidence for such bulk charge modulations, or soft collective charge modes (soft CCMs), in optimally doped Bi_1.5Pb_0.6Sr_1.54CaCu_2O_8+δ (Pb-Bi2212)
... und the summit of the superconducting dome with momentum transfer q_∥∼0.28 reciprocal lattice units (r.l.u.) along the Cu-O bond direction. The signal is stronger at T≃ T_c than at lower temperatures, thereby confirming a competition between soft CCMs and superconductivity. These results demonstrate that soft CCMs are not constrained to the underdoped regime, suggesting that soft CCMs appear across a large part of the phase diagram of cuprates and are intimately entangled with high-T_c superconductivity.