Phase separation at the dimer-superconductor transition in Ir_1−xRh_xTe₂

The detailed evolution of the local atomic structure across the (x, T) phase diagram of Ir_1−xRh_xTe₂ superconductor (0≤x≤0.3, 10K≤T≤300K) is obtained from high-quality x-ray total scattering data using the atomic pair distribution function method. The observed hysteretic thermal structural phase transition from a trigonal to a triclinic dimer phase for low Rh content emphasizes the intimate connection between the lattice and electronic properties. For superconducting samples away from the dimer/superconductor 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 structural phase separation is observed, suggestive of weak first-order character of the Rh-doping 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 imply competition of the dimer and superconducting orders.
[1] R. Yu et al., Phys. Rev. B 98, 134506 (2018).
[2] ] R. Yu et al., Phys. Rev. B 97, 174515 (2018).