Pressure-resistant intermediate valence in Kondo insulator SmB6

TL;DR

This study uses resonant x-ray emission spectroscopy to show that SmB6 maintains an intermediate valence under high pressure, challenging previous assumptions about its electronic state and potential for topological properties.

Contribution

It reveals that SmB6 sustains a stable intermediate valence up to 35 GPa, indicating non-integer valence states persist under pressure, which impacts understanding of its electronic and topological properties.

Findings

f-electron occupancy decreases with pressure

SmB6 retains intermediate valence up to 35 GPa

Pressure-induced gap closure not linked to integer valence stabilization

Abstract

Resonant x-ray emission spectroscopy (RXES) was used to determine the pressure dependence of the f-electron occupancy in the Kondo insulator SmB6. Applied pressure reduces the f-occupancy, but surprisingly, the material maintains a significant divalent character up to a pressure of at least 35 GPa. Thus, the closure of the resistive activation energy gap and onset of magnetic order are not driven by stabilization of an integer valent state. Over the entire pressure range, the material maintains a remarkably stable intermediate valence that can in principle support a nontrivial band structure.