Resonant inelastic x-ray scattering as a probe of band structure effects in cuprates

TL;DR

This paper demonstrates that resonant inelastic x-ray scattering (RIXS) effectively probes the band structure effects in cuprates, revealing insights into excitations above the Fermi surface and explaining material differences.

Contribution

It shows how RIXS can be used to understand band structure effects in cuprates and explains experimental discrepancies through theoretical analysis.

Findings

Good agreement between theory and experiment across doping levels.

RIXS sensitivity to high-energy excitations beyond ARPES.

Material-dependent differences explained by band structure variations.

Abstract

We analyze within quasi-particle theory a recent resonant inelastic x-ray scattering (RIXS) experiment on $\mathrm{YBa_2Cu_3O_{6+x}}$ with the incoming photon energy detuned at several values from the resonance maximum [Minola et al., Phys. Rev. Lett. 114, 217003 (2015)]. Surprisingly, the data shows much weaker dependence on detuning than expected from recent measurements on a different cuprate superconductor, $\mathrm{Bi_2Sr_2CuO_{6+x}}$ [Guarise et al., Nat. Commun. 5, 5760 (2014)]. We demonstrate here, that this discrepancy, originally attributed to collective magnetic excitations, can be understood in terms of the differences between the band structures of these materials. We find good agreement between theory and experiment over a large range of dopings, both in the underdoped and in the overdoped regime. Moreover, we demonstrate that the RIXS signal depends sensitively on excitations at energies well above the Fermi surface, that are inaccessible to traditionally used band structure probes, such as angle-resolved photemisson spectroscopy. This makes RIXS a powerful probe of band structure, not suffering from surface preparation problems and small sample sizes, making it potentially applicable to a number of cuprate materials.