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arXiv · 1801.04874

Unconventional Charge Density Wave Order in the Pnictide Superconductor Ba(Ni$_{1-x}$Co$_x$)$_2$As$_2$

Sangjun Lee·Gilberto de la Pena·Stella X. -L. Sun·Matteo Mitrano·Yizhi Fang·Hoyoung Jang·Jun-Sik Lee·Chris Eckberg·Daniel Campbell·John Collini·Johnpierre Paglione·F. M. F. de Groot·Peter Abbamonte
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Abstract

Ba(Ni$_{1-x}$Co$_x$)$_2$As$_2$ is a structural homologue of the pnictide high temperature superconductor, Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, in which the Fe atoms are replaced by Ni. Superconductivity is highly suppressed in this system, reaching a maximum $T_c$ = 2.3 K, compared to 24 K in its iron-based cousin, and the origin of this $T_c$ suppression is not known. Using x-ray scattering, we show that Ba(Ni$_{1-x}$Co$_x$)$_2$As$_2$ exhibits a unidirectional charge density wave (CDW) at its triclinic phase transition. The CDW is incommensurate, exhibits a sizable lattice distortion, and is accompanied by the appearance of $\alpha$ Fermi surface pockets in photoemission [B. Zhou et al., Phys. Rev. B 83, 035110 (2011)], suggesting it forms by an unconventional mechanism. Co doping suppresses the CDW, paralleling the behavior of antiferromagnetism in iron-based superconductors. Our study demonstrates that pnictide superconductors can exhibit competing CDW order, which may be the origin of $T_c$ suppression in this system.

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Sangjun Lee, Gilberto de la Pena, Stella X. -L. Sun, Matteo Mitrano, Yizhi Fang, Hoyoung Jang, Jun-Sik Lee, Chris Eckberg, Daniel Campbell, John Collini, Johnpierre Paglione, F. M. F. de Groot, Peter Abbamonte. 2018-01-15. Unconventional Charge Density Wave Order in the Pnictide Superconductor Ba(Ni$_{1-x}$Co$_x$)$_2$As$_2$. https://doi.org/10.1103/physrevlett.122.147601

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