Fermi surface reconstruction and multiple quantum phase transitions in the antiferromagnet CeRhIn₅

Conventional, thermally driven continuous phase transitions are described by universal critical behavior that is independent of the specific microscopic details of a material. However, many current studies focus on materials that exhibit quantum-driven continuous phase transitions (quantum critical points, or QCPs) at absolute zero temperature. The classification of such QCPs and the question of whether they show universal behavior remain open issues. Here we report measurements of heat capacity and de Haas-van Alphen (dHvA) oscillations at low temperatures across a field-induced antiferromagnetic QCP (B_c0 ≈ 50 T) in the heavy-fermion metal CeRhIn₅. A sharp, magnetic-field-induced change in Fermi surface is detected both in the dHvA effect and Hall resistivity at B₀ ≈ 30 T, well inside the antiferromagnetic phase. Comparisons with band-structure calculations and properties of isostructural CeCoIn₅ suggest that the Fermi-surface change at B₀ is associated with a localized-to-itinerant transition of the Ce-4f electrons in CeRhIn₅. Taken in conjunction with pressure experiments, our results demonstrate that at least two distinct classes of QCP are observable in CeRhIn₅, a significant step toward the derivation of a universal phase diagram for QCPs.