Evidence of line nodes in superconducting gap function in K2Cr3As3 from specific-heat measurements

We present low-temperature specific-heat measurements of the quasi-one-dimensional superconductors . Our result shows a sharp specific-heat jump around with , which is much larger than the BCS prediction for a weak-coupling superconductor. It indicates that this superconductor is in the strong-coupling regime. After subtracting the lattice contribution and the Schottky anomaly from the total specific-heat data, the low-temperature electronic specific heat is proportional to T2 at different fields and also proportional to at different temperatures below 2.5 K. These results indicate that line nodes are present in the superconducting gap function of .