Nodal superconducting order parameter and thermodynamic phase diagram of (TMTSF)_{2}ClO_{4}

Abstract

The organic materials (TMTSF)2X are unique unconventional superconductors with archetypal quasi-one-dimensional (Q1D) electronic structures. Here, based on our comprehensive field-angle-resolved calorimetry of (TMTSF)2ClO4, we succeeded in mapping the nodal gap structure by discriminating between the Fermi wave vectors and Fermi velocities. In addition, the thermodynamic phase diagrams of (TMTSF)2ClO4 for all principal field directions are obtained. These findings, providing strong evidence of nodal spin-singlet superconductivity, serves as solid bases for the further elucidation of anomalous superconducting phenomena in (TMTSF)2X.