A de Haas–van Alphen experiment under pressure on CeCoIn₅: deviation from the quantum critical region

Abstract

We have carried out a de Haas–van Alphen experiment under pressure on a heavy-fermion superconductor, CeCoIn5. Large cyclotron masses of 15 m0 (m0: the rest mass of an electron) in a nearly cylindrical Fermi surface called αi (i = 1, 2, 3) and 60 m0 in a similar cylindrical Fermi surface called β2 at ambient pressure are found to be strongly reduced to 7 and 40 m0, respectively, at 3 GPa. Correspondingly, the field-dependent cyclotron mass at ambient pressure becomes almost independent of the field at high pressures. These results indicate that CeCoIn5, which is in the vicinity of the quantum critical region at ambient pressure, is changed into a usual heavy-fermion state under high pressures of about 3 GPa.