The effects of copper doping on the structural and superconducting phase transitions of Ba(Ni1−xCux)2As2 were studied by examining the resistivity, magnetic susceptibility, and specific heat. We found an abrupt increase in the superconducting transition temperature Tc from 0.6 K in the triclinic phase with less copper (x ≤ 0.16) to 2.5–3.2 K in the tetragonal phase with more copper (x > 0.16). The specific-heat data suggested that doping-induced phonon softening was responsible for the enhanced superconductivity in the tetragonal phase. All of these observations exhibited striking similarities to those observed in the phosphorus doping of BaNi2(As1−xPx)2 [K. Kudo et al., Phys. Rev. Lett. 109, 097002 (2012).], which markedly contrast the behavior of phosphorus and copper doping of the iron-based superconductor BaFe2As2.
|Publication status||Published - Apr 16 2017|
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