Spin Susceptibility of Noncentrosymmetric Heavy-fermion Superconductor CeIrSi3 under Pressure: 29Si-Knight Shift Study on Single Crystal

TL;DR

This study uses 29Si-NMR to investigate the anisotropic spin susceptibility in the noncentrosymmetric heavy-fermion superconductor CeIrSi3 under pressure, revealing the dominance of Rashba-type spin-orbit interaction below Tc.

Contribution

First experimental observation of anisotropic spin susceptibility below Tc in a noncentrosymmetric superconductor dominated by Rashba spin-orbit interaction.

Findings

Spin susceptibility decreases slightly along the ab-plane below Tc.

No change in spin susceptibility along the c-axis below Tc.

Anisotropy in spin susceptibility is attributed to strong Rashba-type spin-orbit interaction.

Abstract

We report 29Si-NMR study on a single crystal of the heavy-fermion superconductor CeIrSi3 without an inversion symmetry along the c-axis. The 29Si-Knight shift measurements under pressure have revealed that the spin susceptibility for the ab-plane decreases slightly below Tc, whereas along the c-axis it does not change at all. The result can be accounted for by the spin susceptibility in the superconducting state being dominated by the strong antisymmetric (Rashba-type) spin-orbit interaction that originates from the absence of an inversion center along the c-axis and it being much larger than superconducting condensation energy. This is the first observation which exhibits an anisotropy of the spin susceptibility below Tc in the noncentrosymmetric superconductor dominated by strong Rashba-type spin-orbit interaction.