Hall-coefficient diagnostics of the surface state in pressurized SmB6

In this study, we report results of the high-pressure Hall coefficient $({R}_{H})$ measurements in the putative topological Kondo insulator $\mathrm{Sm}{\mathrm{B}}_{6}$ up to 37 GPa. Below 10 GPa, our data reveal that ${R}_{H}(T)$ exhibits a prominent peak upon cooling below 20 K. Remarkably, the temperature at which surface conduction dominates coincides with the temperature of the peak in ${R}_{H}(T)$. The temperature dependent resistance and Hall coefficient can be well fitted by a two-channel model with contributions from the metallic surface and the thermally activated bulk states. When the bulk of $\mathrm{Sm}{\mathrm{B}}_{6}$ becomes metallic and magnetic at $\ensuremath{\sim}10\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, both the ${R}_{H}(T)$ peak and the resistance plateau disappear simultaneously. Our results indicate that the ${R}_{H}(T)$ peak is a fingerprint to diagnose the presence of a metallic surface state in $\mathrm{Sm}{\mathrm{B}}_{6}$. The high-pressure magnetic state of $\mathrm{Sm}{\mathrm{B}}_{6}$ is robust to 180 GPa, and no evidence of superconductivity is observed in the metallic phase.