Resonant Soft X-ray Scattering and the Electron Spectral Function in Cuprates
Resonant soft x-ray scattering (RSXS) is now a widely used method for studying valence band order in strongly correlated materials, some of its notable achievements being the demonstration that stripes in the copper-oxides are charged, the discovery of such order in several materials including YBa2Cu3O7 and "spin ladder" materials such as Sr14Cu24O41, observation of new phenomena at transition metal oxide interfaces, etc.
One of the major outstanding issues with RSXS has been its relationship to more established valence band probes, namely angle-resolved photoemission and scanning tunneling microscopy. These techniques are widely understood as measuring a one-electron spectral function, yet a relationship between RSXS and a spectral function has so far been unclear. In this talk, using some unorthodox arguments that may apply at the oxygen K edge, I will show that RSXS measures the square modulus of an advanced version of the same Green’s function measured with scanning tunneling microscopy.
This observation suggests a reinterpretation of RSXS experiments on stripe materials, previously understood as measuring charge order, as arising from dynamical nesting of the Fermi surface. I will close by discussing the role of excitonic effects and speculating how RSXS might be used to study high energy quasiparticle dynamics not easily accessible to STM or ARPES techniques.
*In collaboration with D. Benjamin, D. Abanin, and E. Demler .