Recently resonant inelastic x-ray scattering (RIXS) has positioned itself as one of the main spectroscopic techniques that is used to understand the complex states of quantum matter [1].
In this talk I will give a brief overview of the RIXS technique and describe the experiments which have contributed to such a huge success of RIXS:

In the first part, I will concentrate on the experimental observation of an orbiton——a collective excitation of a solid which carries solely an orbital quantum number——and
the concomitant separation of the spin and orbital degrees of freedom of an electron in the quasi-one-dimensional copper oxides [2]. Next, in the second part of the talk,
I will discuss how RIXS has observed the collective magnetic excitations in the (doped) copper oxides [3] and how one can understand this phenomenon [4].
I will end the talk by explaining whether this surprising finding could influence the theories of high-temperature superconductivity in these compounds.

REFERENCES

[1] L. J. P. Ament et al., Rev. Mod. Phys. 83, 705 (2011); C. J. Jia et al, Phys. Rev. X 6, 021020 (2016).
[2] J. Schlappa et al., Nature 485, 82 (2012).
[3] M. P. M. Dean et al., Nature Materials 12, 1019 (2013); W. S. Lee et al., Nature Physics 10, 883 (2014); M. Minola, et al., Phys. Rev. Lett. 119, 097001 (2017).
[4] C. J. Jia et al, Nature Communications 5, 3314 (2014); E. Paerschke et al., Physical Review B 99, 205102 (2019).