Pressure dependence of the crystal structure of the strongly correlated bilayer ruthenate Sr3Ru2O7

Ruthenium-oxides are important strongly correlated electron systems: the bilayer ruthenate Sr3Ru2O7 shows field-induced electronic order, while single-layer Sr2RuO4 is an exotic superconductor. Both are highly anisotropic “bad metals”: the resistivity of the conducting planes grows quasi-linearly up to the highest temperatures, while the out-of-plane resistivity at first rises rapidly but then saturates around 100 K. Neither behavior is understood. In recent high pressure measurements we found a puzzling difference between these materials, and we observed a qualitative change in the c-axis resistivity of Sr3Ru2O7 around 5 GPa. In order to understand and then publish this result we are proposing diffraction measurements from 0 to 8 GPa on powder samples of Sr3Ru2O7 to determine the lattice parameters and, especially, to characterize orthorhombic distortions, as a function of pressure.