Anomalous thermal expansion and melting properties of an archetypalf-electron correlated system: Ce

With increasing temperature (T), a rare-earth element, cerium (Ce), exhibits intricate structural phase transitions from fcc-αto dhcp-β, fcc-γ, and bcc-δphases 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 betweenT-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 intriguingV-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 thefelectrons in Ce in realizing the anomalous thermal-expansion behaviors across the different solid and liquid phases at highT.