Large upper critical field in non-centrosymmetric superconductor Y2C3

TL;DR

This study measures the upper critical magnetic field of the non-centrosymmetric superconductor Y2C3, finding it exceeds the Pauli limit, likely due to mixed pairing states caused by broken inversion symmetry.

Contribution

It provides the first detailed measurement of the upper critical field in Y2C3 using two methods, revealing an exceptionally high value above the Pauli limit.

Findings

Upper critical field reaches 30T at zero temperature.

The high critical field exceeds the weak-coupling Pauli limit.

Broken inversion symmetry likely causes mixed pairing states.

Abstract

We determine the upper critical field $\mu_0 H_{c2}(T_c)$ of non-centrosymmetric superconductor $Y_2 C_3$ using two distinct methods: the bulk magnetization M(T) and the tunnel-diode oscillator (TDO) based impedance measurements. It is found that the upper critical field reaches a value of 30T at zero temperature which is above the weak-coupling Pauli paramagnetic limit. We argue that the observation of such a large $\mu_0 H_{c2}(0)$ in $Y_2 C_3$ could be attributed to the admixture of spin-singlet and spin-triplet pairing states as a result of broken inversion symmetry.