Phase evolution of Ce-based heavy-fermion superconductors under compression: A combined first-principles and effective-model study

In many Ce-based superconductors, superconducting (SC) phases emerge or can be tuned in proximity to the antiferromagnetic (AFM) quantum critical point (QCP), but so far the explicit phase evolution near the QCP lacks theoretical understanding. Here, by combing the density functional theory plus dynamical mean-field theory (DFT+DMFT) with effective-model calculations, we provide a theoretical description for Ce-based superconductors under compression. DFT+DMFT calculations for the normal states reveal that the Kondo hybridizations are significantly enhanced under compression, while the initially localized f electrons become fully itinerant via localized-itinerant crossover. We then construct an effective model and show that with the extracted Kondo coupling and RKKY exchange strengths from first-principles calculations, the ground-state phases of these materials can be properly predicted. We also show that the coexistence of magnetic correlation and Kondo hybridization can drive AFM+SC coexisting states in a narrow compression region. Under compression, competition between Kondo and RKKY interactions can drive successive transitions, from the AFM phase to the AFM+SC coexisting phase, then to the paramagnetic SC phase via an AFM transition which generates the QCP, and finally to the normal Kondo paramagnetic (KP) phase through an SC-KP transition induced by the localized-itinerant crossover. Our paper gives proper explanation to the pressure-induced QCP and SC-KP transition and to the phase evolution in pressured Ce-based superconductors, and can help one to understand the SC states around the ferromagnetic quantum transition points in uranium-based superconductors.