Competing Charge/Spin-Stripe and Correlated Metal Phases in Trilayer Nickelates (Pr1-xLax)(4)Ni3O8

Low valent nickelates Rn+1NinO2n+2 (R = rare earth) containing Ni1+ (d9 ) with a quasi-two-dimensional (quasi-2D) square-planar coordination geometry possess structural and electronic properties that are similar to those of high Tc cuprates, including superconductivity itself in the doped infinite-layer (n = infinity) RNiO2 system. Within this Rn+1NinO2n+2 nickelate family, the crystallographic isomorphs Pr4Ni3O8 and La4Ni3O8 exhibit singularly different ground states: Pr4Ni3O8 is metallic, and La4Ni3O8 is a charge- and spin-stripe-ordered insulator. To explore and understand the ground state evolution from metallic Pr4Ni3O8 to stripeordered La4Ni3O8 in the R4Ni3O8 family, we have grown a series of isovalent, substituted single crystals (Pr1-xLax)4Ni3O8. Combining thermodynamic, transport, magnetic, and synchrotron X-ray single crystal diffraction measurements, we reveal a T = 0 transition between metallic and stripe-insulator phase regions, with this putative quantum phase transition at x approximate to 0.45. We propose two possible models for (Pr1-xLax)4Ni3O8: an electronically inhomogeneous system that could serve as a candidate for exploring quantum Griffiths phase physics or a homogeneous system with a clean quantum critical point at the phase boundary