Unfolding the physics of URu2Si2 through Si -> P substitution

The heavy fermion intermetallic compound URu2Si2 exhibits a "hidden-order" phase below the temperature of 17.5 K, which supports both anomalous metallic behavior and unconventional superconductivity. While these individual phenomena have been investigated in detail, it remains unclear how they are related to each other and to what extent uranium f-electron valence fluctuations influence each one. Here we use ligand site substituted URu2Si2-xPx to establish their evolution under electronic tuning. We find that while hidden order is monotonically suppressed and destroyed for x $\leq$ 0.035, the superconducting strength evolves through a dome that is centered near $x$ $\approx$ 0.01 and terminates near $x$ $\approx$ 0.028. This behavior reveals that hidden order depends strongly on tuning outside of the U f-electron shells. It also suggests that while hidden order provides an environment for superconductivity and anomalous metallic behavior, it's fluctuations are not solely responsible for their progression.