We synthesize single crystals of ${\mathrm{PuB}}_4$ using an Al-flux technique. Single-crystal diffraction data provide structural parameters for first-principles density functional theory (DFT) calculations. By computing the density of states, the $Z_2$ topological invariant using the Wilson loop method, and the surface electronic structure from slab calculations, we find that ${\mathrm{PuB}}_4$ is a nonmagnetic strong topological insulator with a band gap of 254 meV. Our magnetic susceptibility, heat capacity, and resistivity measurements are consistent with this analysis, albeit with a smaller gap of 35 meV. DFT plus dynamical mean-field theory calculations show that electronic correlations reduce the size of the band gap, and provide better agreement with the value determined by resistivity. These results demonstrate that ${\mathrm{PuB}}_4$ is a promising actinide material to investigate the interplay of electronic correlations and nontrivial topology.

• Received 18 March 2018

DOI:https://doi.org/10.1103/PhysRevB.97.201114