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.

钌氧化物（Ruthenium-oxides）是一类重要的强关联电子体系（strongly correlated electron systems）：双层钌酸盐Sr₃Ru₂O₇可表现出场致电子有序态（field-induced electronic order），而单层Sr₂RuO₄则是一种奇异超导体（exotic superconductor）。二者均为高度各向异性的“坏金属（bad metals）”：其导电平面（conducting planes）的电阻率可在最高测试温度下保持准线性增长，而面外电阻率（out-of-plane resistivity）起初快速上升，随后在约100开尔文（K）时趋于饱和。目前这两种输运行为均未得到合理解释。在近期的高压测量实验中，我们观测到这两种材料间存在令人困惑的差异，并发现Sr₃Ru₂O₇的c轴电阻率（c-axis resistivity）在约5吉帕斯卡（GPa）处发生了定性变化。为了阐明该实验结果并完成学术发表，我们提议对Sr₃Ru₂O₇的粉末样品开展0至8吉帕斯卡压力区间内的衍射测量（diffraction measurements），以确定其晶格参数（lattice parameters），并重点表征作为压力函数的正交晶畸变（orthorhombic distortions）特性。