Potential Lifshitz transition at optimal substitution in nematic pnictide Ba<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>Ni<sub>2</sub>As<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37851807.
- Also identified by DOI 10.1126/sciadv.adi4966 and PMC identifier 10584352.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
BaNi<sub>2</sub>As<sub>2</sub> is a structural analog of the pnictide superconductor BaFe<sub>2</sub>As<sub>2</sub>, 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 (<i>T<sub>c</sub></i>). To understand the mechanisms responsible for enhancement of <i>T<sub>c</sub></i>, we present high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements of the Ba<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>Ni<sub>2</sub>As<sub>2</sub> 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 <i>T<sub>c</sub></i> is maximum. These nested pockets host Ni <i>d<sub>xz</sub>/d<sub>yz</sub></i> 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 <i>T<sub>c</sub></i>.