Electronic correlations and topology in Kondo insulator PuB${}_6$

Utilizing a combination of dynamical mean field theory and density functional theory (DMFT/DFT), it has been theoretically proposed that PuB${}_6$ is a strongly correlated topological insulator characterized by nontrivial ${\mathbf{Z}}_2$ topological invariants and metallic surface states ($\mathit{\text{X.}}\mathit{\text{Deng}}\mathit{\text{et}}\mathit{\text{al.,}}\mathit{\text{Phys.}}\mathit{\text{Rev.}}\mathit{\text{Lett.}}\mathit{\text{111,}}\mathit{\text{176404}}\mathit{\text{(2013)}}$). Here, we demonstrate through low-temperature magneto-transport measurements and first-principles calculations that PuB$6$ exhibits characteristics of a topological Kondo insulating state. These features include a transition in electrical resistivity from high-temperature, thermally activated behavior with a narrow gap at the Fermi level ($\mathrm{\Delta }\rho \sim$ 20 meV) to a distinctive low-temperature plateau, as well as a surface-to-volume dependence of electrical resistivity at low temperatures. The topological nature of PuB${}_6$ is further supported by the theoretical calculations, which show that GGA+$U$ is capable of capturing electronic, topological, and lattice properties of PuB${}_6$ with much lower computational cost than DMFT.