Electronic superlattice revealed by resonant scattering from random impurities in Sr3Ru2O7

TL;DR

This paper demonstrates that resonant elastic x-ray scattering at impurity absorption edges can detect superlattice orders in complex oxides, overcoming previous limitations in sensitivity and periodicity detection.

Contribution

It introduces a novel impurity-based resonant scattering method that extends the capabilities of REXS for studying subtle superlattice structures.

Findings

Impurities can serve as effective probes for superlattice detection.

Simulations and experiments on Sr3Ru2O7 show enhanced sensitivity.

Method extends REXS applicability to smaller superlattice amplitudes.

Abstract

Resonant elastic x-ray scattering (REXS) is an exquisite element-sensitive tool for the study of subtle charge, orbital, and spin superlattice orders driven by the valence electrons, which therefore escape detection in conventional x-ray diffraction (XRD). Although the power of REXS has been demonstrated by numerous studies of complex oxides performed in the soft x-ray regime, the cross section and photon wavelength of the material-specific elemental absorption edges ultimately set the limit to the smallest superlattice amplitude and periodicity one can probe. Here we show -- with simulations and REXS on Mn-substituted Sr$_3$Ru$_2$O$_7$ -- that these limitations can be overcome by performing resonant scattering experiments at the absorption edge of a suitably-chosen, dilute impurity. This establishes that -- in analogy with impurity-based methods used in electron-spin-resonance, nuclear-magnetic resonance, and M\"ossbauer spectroscopy -- randomly distributed impurities can serve as a non-invasive, but now momentum-dependent probe, greatly extending the applicability of resonant x-ray scattering techniques.