Zero-field Quantum Critical Point in CeCoIn5
Abstract
Quantum criticality in the normal and superconducting state of the heavy-fermion metal CeCoIn5 is studied by measurements of the magnetic Gr\"uneisen ratio, H, and specific heat in different field orientations and temperatures down to 50 mK. Universal temperature over magnetic field scaling of H in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.
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