Anomalous Spin Response in the Non-Centrosymmetric Metal CePt3Si

Non-centrosymmetric metals with tetragonal structure are characterized by an antisymmetric Rashba-type spin-orbit interaction, which has been predicted to give rise to anomalous spin susceptibility. Our polarized inelastic neutron scattering measurements in the normal phase of the heavy-fermion superconductor CePt3 Si confirm this prediction. We find that for a finite wave vector along the crystallographic a-direction the spin susceptibility chi(aa) is different from chi(bb) by a factor of two. The effect is even larger than in theoretical calculations based on the Hubbard model, and we speculate that this is due to the strong spin-orbit coupling of rare-earth heavy fermions.