Specific heat measurements of organic superconductivity in (TMTSF) 2ClO4

Abstract

The specific heat of the organic superconductor (TMTSF)2ClO 4 has been measured between 0.4 and 2 K. A large anomaly of the electronic contribution at 1.22 K has been attributed to the onset of three-dimensional superconducting order. There is a large magnetic field dependence of the electronic contribution above 1.22 K which is not characteristic of a normal conducting state. The application of a magnetic field of 63 kOe along the c*-axis of the single crystals restores a ground state exhibiting a very low density of states at the Fermi level (a narrow gap semiconducting or a semimetallic state). A phase transition towards a conducting state with a finite density of states at Fermi level is visible around 1.4 K. Our specific heat results support the existence of a wide 1-D superconducting fluctuating regime.