A Drastic Change of the Fermi Surface at a Critical Pressure in CeRhIn₅: dHvA Study under Pressure

Abstract

We carried out the de Haas–van Alphen (dHvA) experiment for an antiferromagnet CeRhIn 5 at high pressures up to 3 GPa. The cross-sectional areas of the Fermi surfaces due to main dHvA branches α i and β 2 at ambient pressure, which are well explained by two kinds of nearly cylindrical Fermi surfaces of a non-4 f reference compound LaRhIn 5 , are unchanged up to about 2.3 GPa, while the corresponding cyclotron masses m c * increase steeply above a pressure P * = 1.6 GPa where pressure-induced superconductivity sets in : m * c = 5.5 m 0 at ambient pressure, 20 m 0 at 1.6 GPa and 60 m 0 at 2.2 GPa for branch β 2 , for example. Above 2.4 GPa, new dHvA branches appear, which are in good agreement with the corresponding dHvA branches of a 4 f -itinerant heavy fermion superconductor CeCoIn 5 , indicating that the 4 f electron of CeRhIn 5 becomes itinerant and significantly contributes to the volume of the Fermi surface. The 4 f -electron character is thus changed from localized to itinerant at a critical pressure P c ≃2.35 GPa, where the superconducting transition temperature becomes a maximum.