Potential Lifshitz transition at optimal substitution in nematic pnictide Ba_1-xSr_xNi₂As₂.

ABSTRACT: BaNi₂As₂ is a structural analog of the pnictide superconductor BaFe₂As₂, which, like the iron-based superconductors, hosts a variety of ordered phases including charge density waves (CDWs), electronic nematicity, and superconductivity. Upon isovalent Sr substitution on the Ba site, the charge and nematic orders are suppressed, followed by a sixfold enhancement of the superconducting transition temperature (T_c). To understand the mechanisms responsible for enhancement of T_c, we present high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements of the Ba_1-xSr_xNi₂As₂ series, which agree well with our density functional theory (DFT) calculations throughout the substitution range. Analysis of our ARPES-validated DFT results indicates a Lifshitz transition and reasonably nested electron and hole Fermi pockets near optimal substitution where T_c is maximum. These nested pockets host Ni d_xz/d_yz orbital compositions, which we associate with the enhancement of nematic fluctuations, revealing unexpected connections to the iron-pnictide superconductors. This gives credence to a scenario in which nematic fluctuations drive an enhanced T_c.

SUBMITTER: Narayan DM 

PROVIDER: S-EPMC10584352 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature