Spectral Evidence for Unidirectional Charge Density Wave in Detwinned BaNi${}_2$As${}_2$

Abstract

The emergence of unconventional superconductivity in proximity to intertwined electronic orders is especially relevant in the case of iron-based superconductors. Such order consists of an electronic nematic order and a spin density wave in these systems. BaNi${}_2$As${}_2$, like its well-known iron-based analog BaFe${}_2$As${}_2$, also hosts a symmetry-breaking structural transition that is coupled to a unidirectional charge density wave (CDW), providing a novel platform to study intertwined orders. Here, through a systematic angle-resolved photoemission spectroscopy study combined with a detwinning $B_{1}g$ uniaxial strain, we identify distinct spectral evidence of band evolution due to the structural transition as well as CDW-induced band folding. In contrast to the nematicity and spin density wave in BaFe${}_2$As${}_2$, the structural and CDW order parameters in BaNi${}_2$As${}_2$ are observed to be strongly coupled and do not separate in the presence of uniaxial strain. Our measurements point to a likely lattice origin of the CDW in BaNi${}_2$As${}_2$.

6 pages, 4 figures

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Cited by in corpus (1)

• Potential Lifshitz transition at optimal substitution in nematic pnictide Ba${}_{1-x}$Sr${}_x$Ni${}_2$As${}_2$