Strain-induced orbital-energy shift in antiferromagnetic RuO2 revealed by resonant elastic x-ray scattering

In its ground state, RuO2 was long thought to be an ordinary metallic paramagnet. Recent neutron and x-ray diffraction revealed that bulk RuO2 is an antiferromagnet with TN above 300 K. Furthermore, epitaxial strain induces superconductivity in thin films of RuO2 below 2 K. Here, we present a resonant elastic x-ray scattering study at the Ru L2 edge of the strained RuO2 films exhibiting the strain-induced superconductivity. We observe an azimuthal modulation of the 100 Bragg peak consistent with bulk. Most notably, in the strained films displaying superconductivity, we observe a similar to 1 eV shift of the Ru eg orbitals to a higher energy. The energy shift is smaller in thicker, relaxed films and films with a different strain direction. Our results provide further evidence of the utility of epitaxial strain as a tuning parameter in complex oxides.

Automated summary

In its ground state, RuO2 was previously thought to be an ordinary metallic paramagnet, but recent research has revealed that RuO2 is actually an antiferromagnet and can exhibit superconductivity under epitaxial strain. A resonant elastic x-ray scattering study found a shift in the energy of the Ru eg orbitals in strained RuO2 films.