Heavy‐fermion superconductivity and Fermi‐surface properties under pressure

Abstract We present an overview of the Fermi‐surface properties for antiferromagnets CeRh 2 Si 2 , CeIn 3 , CeRhIn 5 , and CeIrSi 3 , which were clarified from the de Haas–van Alphen (dHvA) experiments under strong magnetic fields up to 170 kOe and high pressures up to 3 GPa. A drastic change of the 4f‐electronic state from a 4f‐localized Fermi surface to a 4f‐itinerant Fermi surface occurs in CeRh 2 Si 2 , CeIn 3 , and CeRhIn 5 when the pressure P crosses a critical pressure P c or $P_{{\rm c}}^{*} $ . Here, the Néel temperature T N disappears and the superconducting state appears at around P c or $P_{{\rm c}}^{*} $ . A critical pressure $P_{{\rm c}}^{*} $ in CeRhIn 5 is the pressure when T N is extrapolated to zero in the temperature vs. pressure phase diagram, and/or the antiferromagnetic state disappears completely even in magnetic fields. This is because the antiferromagnetic state is stable against magnetic fields, or in other words, the antiferromagnetic state recovers in magnetic fields. CeIrSi 3 without inversion symmetry in the tetragonal structure is also similar to CeRhIn 5 in the superconducting and Fermi‐surface properties. It is characteristic that a huge upper critical field at zero temperature in superconductivity $H_{{\rm c2}} (0) \simeq 450\,{\rm kOe}$ is realized for $H{\parallel} [001]$ in CeIrSi 3 with the superconducting transition temperature T sc  = 1.6 K.