Tunneling break-junction measurements of the superconducting gap in Y2C3

Tunneling measurements of the electron spectrum in the superconducting state have been carried out in Y2C3 samples with the bulk (resistive and diamagnetic) critical temperature Tc = 15–16 K. A break-junction technique was crucial to find the intrinsic gap features. The representative gap structure at 4 K reveals distinct BCS-like peaks with the gap value of 2Δ(4 K) = 3–4 meV. Assuming local Tc values of 10–13 K, the characteristic gap to Tc ratio 2Δ/kBTc (kB is the Boltzmann constant) was found to possess the BCS weak-coupling value 3.5 ± 0.2, appropriate to isotropic s-wave superconductors.

► The first electron tunneling measurements of the superconductor Y2 C3 are carried out. ► The break-junction tunneling is crucial to find the gap of the unstable Y2C3. ► The simple BCS gap structure in Y2C3 is confirmed by the break-junction method. ► There is no evidence of the multiple-gap superconductivity in Y2C3.