Hidden magnetism and quantum criticality in the heavy fermion superconductor CeRhIn5

• Published in: Nature 2006-03, Vol.440 (7080), p.65-68
• Main Authors: Park, Tuson, Ronning, F., Yuan, H. Q., Salamon, M. B., Movshovich, R., Sarrao, J. L., Thompson, J. D.
• Format: Article
• Language: English
• Subjects: Boundaries; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Copper; Exact sciences and technology; Fluctuations; Heavy-fermion superconductors; Humanities and Social Sciences; letter; Magnetic fields; Magnetic properties; Magnetism; multidisciplinary; Oxides; Particle physics; Physics; Properties of type I and type II superconductors; Quantum theory; Science; Science (multidisciplinary); Superconducting materials (excluding high-tc compounds); Superconductivity; Superconductors; Transition temperatures
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature04571

With only a few exceptions that are well understood, conventional superconductivity does not coexist with long-range magnetic order (for example, ref. 1 ). Unconventional superconductivity, on the other hand, develops near a phase boundary separating magnetically ordered and magnetically disordered phases 2 , 3 . A maximum in the superconducting transition temperature T c develops where this boundary extrapolates to zero Kelvin, suggesting that fluctuations associated with this magnetic quantum-critical point are essential for unconventional superconductivity 4 , 5 . Invariably, though, unconventional superconductivity masks the magnetic phase boundary when T < T c , preventing proof of a magnetic quantum-critical point 5 . Here we report specific-heat measurements of the pressure-tuned unconventional superconductor CeRhIn 5 in which we find a line of quantum–phase transitions induced inside the superconducting state by an applied magnetic field. This quantum-critical line separates a phase of coexisting antiferromagnetism and superconductivity from a purely unconventional superconducting phase, and terminates at a quantum tetracritical point where the magnetic field completely suppresses superconductivity. The T → 0 K magnetic field–pressure phase diagram of CeRhIn 5 is well described with a theoretical model 6 , 7 developed to explain field-induced magnetism in the high- T c copper oxides, but in which a clear delineation of quantum–phase boundaries has not been possible. These experiments establish a common relationship among hidden magnetism, quantum criticality and unconventional superconductivity in copper oxides and heavy-electron systems such as CeRhIn 5 .