English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We measured high resolution Cu $L_3$ edge resonant inelastic x-ray scattering(RIXS) of the undoped cuprates La$_2$CuO$_4$, Sr$_2$CuO$_2$Cl$_2$, CaCuO$_2$and NdBa$_2$Cu$_3$O$_6$. The dominant spectral features were assigned to $dd$excitations and we extensively studied their polarization and scatteringgeometry dependence. In a pure ionic picture, we calculated the theoreticalcross sections for those excitations and used them to fit the experimental datawith excellent agreement. By doing so, we were able to determine the energy andsymmetry of Cu-3$d$ states for the four systems with unprecedented accuracy andconfidence. The values of the effective parameters could be obtained for thesingle ion crystal field model but not for a simple two-dimensional clustermodel. The firm experimental assessment of $dd$ excitation energies carriesimportant consequences for the physics of high $T_c$ superconductors. On onehand, having found that the minimum energy of orbital excitation is always$\geq 1.4$ eV, i.e., well above the mid-infrared spectral range, leaves tomagnetic excitations (up to 300 meV) a major role in Cooper pairing incuprates. On the other hand, it has become possible to study quantitatively theeffective influence of $dd$ excitations on the superconducting gap in cuprates.

Energy and symmetry of $dd$ excitations in undoped layered cuprates measured by Cu $L_3$ resonant inelastic x-ray scattering