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

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, $d{\nu }_{\alpha \alpha }\mathrm{/}dP$, at $P_{c1}=1.75$ GPa. These changes to these coupling constants reflect alterations to the electronic structure at the quantum critical point.