Evolution of hyperfine parameters across a quantum critical point in CeRhIn$_5$

Abstract

We report Nuclear Magnetic Resonance (NMR) data for both the In(1) and In(2) sites in the heavy fermion material CeRhIn$_5$ under hydrostatic pressure. The Knight shift data reveal a suppression of the hyperfine coupling to the In(1) site as a function of pressure, and the electric field gradient, $\nu_{\alpha\alpha}$, at the In(2) site exhibits a change of slope, $d\nu_{\alpha\alpha}/dP$, at $P_{c1} = 1.75$ GPa. These changes to these coupling constants reflect alterations to the electronic structure at the quantum critical point.