Topological phase transition in the archetypal f -electron correlated system of cerium

A typical $f$-electron Kondo lattice system Ce exhibits a well-known isostructural transition, the so-called $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\alpha}$ transition, accompanied by an enormous volume collapse. Most interestingly, we have discovered that a topological phase transition also takes place in elemental Ce, concurrently with the $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\alpha}$ transition. Based on the dynamical mean-field theory approach combined with density functional theory, we have unraveled that the nontrivial topology in $\ensuremath{\alpha}$-Ce is driven by the $f\ensuremath{-}d$ band inversion, which arises from the formation of a coherent $4f$ band around the Fermi level. We captured the formation of the $4f$ quasiparticle band that is responsible for the Lifshitz transition and the nontrivial ${\mathrm{Z}}_{2}$ topology establishment across the phase boundary. This discovery provides a concept of a ``topology switch'' for topological Kondo systems. The ``on'' and ``off'' switching knob in Ce is versatile in a sense that it is controlled by the available pressure ($\ensuremath{\lesssim}1$ GPa) at room temperature.