High pressure induced superconductivity and chirality-neutral Fermi surface in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>SrS</mml:mi><mml:msub><mml:mi mathvariant="normal">i</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:

In this study, we investigate the electronic structure and topological properties of the compound <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>SrS</a:mi><a:msub><a:mi mathvariant="normal">i</a:mi><a:mn>2</a:mn></a:msub></a:mrow></a:math> using angle-resolved photoemission spectroscopy (ARPES), electrical transport measurements, and calculations. In contrast to recent theoretical predictions that <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>SrS</c:mi><c:msub><c:mi mathvariant="normal">i</c:mi><c:mn>2</c:mn></c:msub></c:mrow></c:math> is a Weyl semimetal with robust Weyl nodes and Fermi arcs, our ARPES measurements on undoped and Ca-doped <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mi>SrS</e:mi><e:msub><e:mi mathvariant="normal">i</e:mi><e:mn>2</e:mn></e:msub></e:mrow></e:math> single crystals show no evidence of the predicted Weyl fermions or Fermi arcs at ambient pressure. Instead, ARPES and transport data show that <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mi>SrS</g:mi><g:msub><g:mi mathvariant="normal">i</g:mi><g:mn>2</g:mn></g:msub></g:mrow></g:math> is a narrow-gap semiconductor at ambient conditions. Our hybrid functional calculations also find a small band gap, in agreement with experiments. However, by applying external pressure, we induce a topological phase transition where the electronic bands overlap and Weyl nodes appear, as confirmed by transport measurements and calculations. Interestingly, we also observe a pressure-induced superconducting transition above 20 GPa. Our results establish <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:mrow><i:mi>SrS</i:mi><i:msub><i:mi mathvariant="normal">i</i:mi><i:mn>2</i:mn></i:msub></i:mrow></i:math> as a platform to study the interplay between topological states and superconductivity driven by external pressure. Importantly, our results challenge the previously predicted intrinsic Weyl semimetallic nature of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mi>SrS</k:mi><k:msub><k:mi mathvariant="normal">i</k:mi><k:mn>2</k:mn></k:msub></k:mrow></k:math> and highlight the need for combined experimental and advanced computational approaches to correctly describe the complex electronic structures in topological materials. Published by the American Physical Society 2024