The Hall coefficient R_H of Sr₂RuO₄ exhibits a non-monotonic temperature dependence with two sign reversals. We show that this puzzling behavior is the signature of two crossovers, which are key to the physics of this material. The increase of R_H and the first sign change upon cooling are associated with a crossover into a regime of coherent quasiparticles with strong orbital differentiation of the inelastic scattering rates. The eventual decrease and the second sign change at lower temperature are driven by the crossover from inelastic to impurity-dominated scattering. This qualitative picture is supported by quantitative calculations of R_H(T) using the Boltzmann transport theory in combination with dynamical mean-field theory, taking into account the effect of spin–orbit coupling. Our insights shed new light on the temperature dependence of the Hall coefficient in materials with strong orbital differentiation, as observed in Hund’s metals.

Sr ₂ RuO ₄的霍尔系数R _H表现出非单调温度依赖性，具有两个符号反转。我们证明了这种令人费解的行为是两个交叉的标志，这是这种材料的物理特性的关键。R _H的增加和冷却时的第一符号变化与进入具有非弹性散射速率的强轨道区分的相干准粒子的状态有关。从非弹性散射到以杂质为主的散射的转变驱动了最终的降低和在较低温度下的第二符号变化。这种质图像是通过定量计算的支持- [R _ħ（Ť），将玻尔兹曼输运理论与动力学平均场理论相结合，同时考虑了自旋-轨道耦合的影响。正如在洪德的金属中所观察到的那样，我们的见解为具有强轨道分化的材料中霍尔系数对温度的依赖性提供了新的线索。