Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

5 years ago

Dispersive charge density wave excitations in Bi2Sr2CaCu2O8+δ

L. Braicovich, Y. Yoshida, M. Hashimoto, T. P. Devereaux, Y. Y. Peng, N. B. Brookes, K. Kummer, L. Chaix, Z.-X. Shen, H. Eisaki, G. Ghiringhelli, W.-S. Lee, Y. He, S. Ishida, M. Salluzzo, S. Chen, B. Moritz

With sufficient energy resolution, resonant inelastic X-ray scattering (RIXS) can be an ideal probe for revealing the CDW excitations in cuprates. By tuning the incident photon energy to the Cu L₃-edge (Fig. 1a), the resonant absorption and emission processes can leave the system in excited final states, which couple to a variety of excitations arising from orbital, spin, charge, and lattice degrees of freedom¹⁵. Thus, information of these elementary excitations in energy and momentum space can be deduced from analysing the RIXS spectra as functions of the energy loss and the momentum transfer of the photons (Fig. 1a). This is highlighted by the pivotal role that RIXS has recently played in revealing orbital and magnetic excitations in cuprates^{16, 17, 18, 19, 20}. In addition, RIXS provided the first X-ray scattering evidence for an incommensurate CDW in (Y, Nd)Ba₂Cu₃O_6+δ (ref. 4), owing to energy resolution that separated the quasi-elastic CDW signal (bright spot in Fig. 1b, limited by the instrumental resolution ~130 meV) from other intense higher-energy excitations. Notably this quasi-elastic signal is asymmetric with respect to zero energy loss (Fig. 1c), which indicates the possible existence of additional low-energy excitations near the CDW wavevector (Q_CDW).

Publisher URL: http://dx.doi.org/10.1038/nphys4157

DOI: 10.1038/nphys4157