Exploring the Dirac nature of RbBi2

Abstract

Characteristics of topological semimetals such as a nonsaturating magnetoresistance (MR), a field-induced metal to semiconducting crossover and a robust resistivity plateau are observed under a magnetic field in type-I ${\mathrm{RbBi}}_{2}$ bulk superconductor with ${T}_{\mathrm{c}}=4.15$ K. The MR exhibits a notable 3500% increase at 2 K and 9 T and the resistivity follows a power law temperature dependence, while the MR $\ensuremath{\propto}\phantom{\rule{4pt}{0ex}}{H}^{1.26}$, indicating weak carrier compensation. First principles calculations provided insights into the dynamical stability of the cubic structure at 0 K. Both hole and electron pockets are observed at the Fermi surface. The electron-phonon interaction constant indicates weak coupling strength ($<1$) that leads to a maximum predicted ${T}_{\mathrm{c}}$ of 2.852 K. Just below the Fermi level, ${\mathrm{E}}_{F}$, the electronic band structure consists of linear band crossings at the $X$ points in the Brillouin zone (BZ) corresponding to massless, symmetry-protected Dirac fermions.