Emil Bozin1,Runze Yu1,Soham Banerjee1,2,Hechang Lei1,Ryan Sinclair3,Milinda Abeykoon1,Haidong Zhou3,Cedomir Petrovic1,Zurab Guguchia1,2
Brookhaven National Laboratory1,Columbia University2,The University of Tennessee, Knoxville3
Emil Bozin1,Runze Yu1,Soham Banerjee1,2,Hechang Lei1,Ryan Sinclair3,Milinda Abeykoon1,Haidong Zhou3,Cedomir Petrovic1,Zurab Guguchia1,2
Brookhaven National Laboratory1,Columbia University2,The University of Tennessee, Knoxville3
The material IrTe<sub>2</sub> exhibits a transition to a modulated state featuring Ir-Ir dimers, with large associated atomic displacements. Partial substitution of Pt or Rh for Ir destabilizes the modulated structure and induces superconductivity. It has been proposed that quantum critical dimer fluctuations might be associated with the superconductivity. Here we test for such local dimer correlations and demonstrate their absence. X-ray pair distribution function (PDF) approach reveals that the local structure of Ir<sub>0.95</sub>Pt<sub>0.05</sub>Te<sub>2</sub> and Ir<sub>0.8</sub>Rh<sub>0.2</sub>Te<sub>2</sub> dichalcogenide superconductors with compositions just past the dimer/superconductor boundary is explained well by a dimer-free model down to 10 K, ruling out the possibility of there being nanoscale dimer fluctuations in this regime. This is inconsistent with the proposed quantum-critical-point-like interplay of the dimer state and superconductivity, and precludes scenarios for dimer fluctuations mediated superconducting pairing.<br/><br/>On the other hand, the detailed evolution of the local atomic structure across the (x, T) phase diagrams of the two superconducting families, Ir<sub>1−x</sub>Rh<sub>x</sub>Te<sub>2</sub> (0≤x≤0.3) and Ir<sub>1−x</sub>Pt<sub>x</sub>Te<sub>2</sub> (0≤x≤0.05) in 10K≤T≤300K range, reveal hysteretic thermal structural phase transition from a trigonal (P-3m1) to a triclinic (P-1) dimer phase for low Pt and Rh contents. This emphasizes the intimate connection between the lattice and electronic properties. For superconducting samples away from the dimer/superconductor phase boundary, structural transition is absent and the local structure remains trigonal down to 10 K. In the narrow range of compositions close to the boundary, PDF analysis reveals structural phase separation, suggestive of weak first-order character of the substitution induced dimer-superconductor quantum phase transition. Samples from this narrow range show weak anomalies in electronic transport and magnetization, hallmarks of the dimer phase, as well as superconductivity albeit with incomplete diamagnetic screening. The results suggest that the dimer and superconducting orders exist in the mutually exclusive spatial regions.