Potential Lifshitz transition at optimal substitution in nematic pnictide Ba1-xSrxNi2As2

• Published in: Science advances Vol. 9; no. 42; p. eadi4966
• Main Authors: Narayan, Dushyant M, Hao, Peipei, Kurleto, Rafał, Berggren, Bryan S, Linn, A Garrison, Eckberg, Christopher, Saraf, Prathum, Collini, John, Zavalij, Peter, Hashimoto, Makoto, Lu, Donghui, Fernandes, Rafael M, Paglione, Johnpierre, Dessau, Daniel S
• Format: Journal Article
• Language: English
• Published: American Association for the Advancement of Science 20.10.2023
• Subjects: Condensed Matter Physics; Physical and Materials Sciences; SciAdv r-articles
• ISSN: 2375-2548
• DOI: 10.1126/sciadv.adi4966

BaNi 2 As 2 is a structural analog of the pnictide superconductor BaFe 2 As 2 , 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− x Sr x Ni 2 As 2 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 . Electronic structure of Ba1−xSrxNi2As2 is investigated through the Sr substitution range.