Anomalous thermal expansion and melting properties of an archetypal <i>f</i>-electron correlated system: Ce

With increasing temperature (<i>T</i>), a rare-earth element, cerium (Ce), exhibits intricate structural phase transitions from fcc-<i>α</i>to dhcp-<i>β</i>, fcc-<i>γ</i>, and bcc-<i>δ</i>phases before reaching the liquid phase. Interestingly, Ce exhibits abnormal thermal-expansion behavior (either positive or negative) with respect to the temperature change, which is associated with each structural transition. Focusing on the interplay between<i>T</i>-dependent electronic and structural degrees of freedom, we have investigated the underlying mechanism of peculiar thermal-expansion properties of Ce, which are quite distinct from those of La, Pr, and Nd. We have also explored the unusual melting physics in Ce, including the intriguing<i>V</i>-shaped melting curve as well as the negative thermal-expansion phenomenon upon melting. We propose two possible scenarios for the melting mechanism, Mott- and promotional-model-based ones, both of which highlight the essential role of the<i>f</i>electrons in Ce in realizing the anomalous thermal-expansion behaviors across the different solid and liquid phases at high<i>T</i>.