Observation of Charge Density Waves in Superconducting Ba(Ni<sub>1-x</sub>Co<sub>x</sub>)<sub>2</sub>As<sub>2</sub>
ORAL
Abstract
Nickel-pnictide compounds exhibit superconductivity at relatively low Tc, compared to isostructural iron-pnictide high-Tc superconductors. As an example, BaNi2As2, a non-magnetic analogue of BaFe2As2, has Tc of 0.7 K and Co-substitution raises it up to 2.5 K, whereas Tc of BaFe2As2 can be as high as 38 K upon doping. This strong suppression of the superconductivity in BaNi2As2 suggests the possible existence of competing phases. Here, we present the first observation of charge density wave (CDW) order in BaNi2As2. Using x-ray reciprocal space mapping, we observed an incommensurate CDW below 148 K in tetragonal phase and a commensurate CDW below 128 K in triclinic phase. On Co-substitution, the onset of the CDW is suppressed to 70 K at x=0.07 and 0.08, and completely suppressed at x=0.12. We also observe that CDW order is strongly tied to the tetragonal to triclinic phase transition, implying a role of the structural distortion in stabilizing the electronic ordering. These results prove the existence of novel ordered phases in Ni-based superconductors and support a competing order scenario for the coexistence of charge order and superconductivity in nickel-pnictide materials.
*This work was supported by DOE Office of Basic Energy Sciences grant no. DE-FG02-06ER46285
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Presenters
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Sangjun Lee
- Physics/MRL, Univ of Illinois - Urbana
- Univ of Illinois - Urbana
- Department of Physics, University of Illinois