Huge Upper Critical Field and Electronic Instability in Pressure-induced Superconductor CeIrSi3without Inversion Symmetry in the Crystal Structure

Abstract

We measured low-temperature electrical resistivity in a magnetic field as a function of pressure, and studied the superconducting property of CeIrSi 3 with a non-centrosymmetric tetragonal structure. CeIrSi 3 is an antiferromagnet with a Neel temperature T N = 5.0 K at ambient pressure, but the antiferromagnetic ordering disappears completely at a pressure P c = 2.25 GPa. Superconductivity appears in a wide pressure region from 1.8 to about 3.5 GPa, with a maximum transition temperature T sc ≃1.6 K at P c * ≃2.63 GPa. At around P c * , the upper critical field H c2 for the magnetic field H along the [0 0 1] direction is not destroyed by spin polarization based on Zeeman coupling but possesses an upturn curvature below 1 K, revealing a divergent tendency of H c2 at P c * , with a huge H c2 (0)≃450 kOe. On the other hand, the upper critical field for H ∥[1 1 0] indicates the tendency of Pauli paramagnetic suppression, with H c2 (0) = 95 kOe at 2.65 GPa. This might be a combined phenomenon between the electr...