Fluctuation-Driven First-Order Transition in Pauli-Limited d-Wave Superconductors

摘要

Recently, the presence of a kind of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in a heavy fermion superconductor CeCoIn_5 at low temperatures in a field H parallel to the superconducting layers (H ⊥ c) has been clarified through thermodynamic and ultrasound measurements. Dalidovich and Yang (DY) have argued by assuming the Pauli limiting, i.e., neglecting the presence of vortices, that a fluctuation-driven first-order transition (FOT) resulting from their perturbative renormalization-group analysis is consistent with the apparent FOT near H_(c2)(T) between the normal and FFLO states in CeCoIn_5. On the other hand, the observed anomaly in the sound velocity seems to be consistent only with a change of tilt elasticity of vortices due to a growth of a modulation parallel to H.