The persistence of the intermediate valence in SmB₆ under pressure

We measured resonant x-ray emission spectroscopy (RXES) on SmB₆ to determine the pressure dependence of the Sm f-electron occupancy. Although pressure reduces the f-occupancy, the material does not become trivalent even at the highest measured pressures of 35 GPa. Indeed, ovver the entire pressure range, Sm maintains a remarkably stable intermediate valence. This result implies that the pressure-driven closure of the hybridization/energy gap and onset of magnetic order do not require the stabilization of an integer valent state. I will discuss the implications of our results in regard to nontrivial band structure.