Absence of Local Fluctuating Dimers in Superconducting Ir_1-x(Pt,Rh)_xTe₂

The local atomic structure of Ir_0.96Pt_0.04Te₂ and Ir_0.8Rh_0.2Te₂ dichalcogenide superconductors at10 K and away from the Ir-Ir dimer/superconductor boundary is examined by x-ray total scattering based pair distribution function (PDF) approach. Hypothesis that dimer fluctuations persist in the superconducting compositional range, which would leave footprints in the local structure, is tested by qualitative PDF analysis and explicit modeling of the experimental data. Trigonal dimer-free local structure model explains the PDF data well, ruling out the possibility of nanoscale dimer fluctuations in this regime. In the vicinity of the dimer/superconductor boundary PDF evidences trigonal/triclinic phase separation, compatible with weakly first order character of the dimer-superconductor transition. Observations are inconsistent with proposed quantum-critical-point-like competition of the dimer state and superconductivity, and preclude scenarios for dimer fluctuations mediated superconducting pairing. Local structure of IrTe₂ at 300 K conforms to the same dimer-free model, which is at odds with dimer order-disorder description of the intriguing electronic/structural transition seen in the endmember.