Feedback of superconductivity on the magnetic excitation spectrum of UTe${}_2$

Abstract

We investigate the spin dynamics in the superconducting phase of UTe${}_2$ by triple-axis inelastic neutron scattering on a single crystal sample. At the wave-vector ${\mathbf{k}}_1$=(0, 0.57, 0), where the normal state antiferromagnetic correlations are peaked, a modification of the excitation spectrum is evidenced, on crossing the superconducting transition, with a reduction of the relaxation rate together with the development of an inelastic peak at $\hat{I}\text{c◯}$ $\approx$ 1 meV. The low dimensional nature and the the $a$-axis polarization of the fluctuations, that characterise the normal state, are essentially maintained below $T_{sc}$. The high ratio $\hat{I}\text{c◯}/k_B{T}_{sc}$ $\approx$ 7.2 contrasts with the most common behaviour in heavy fermion superconductors.

3 figures, 1 table