Enhancement of superconducting transition temperature and exotic stoichiometries in the Lu−S system under high pressure

Binary metal sulfides are a potential family of materials for exploring high <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>T</a:mi><a:mi mathvariant="normal">c</a:mi></a:msub></a:math> superconductors under high pressure. In this work, we study the crystal structures, electronic structures, and superconducting properties of the Lu-S system in the pressure range from 0 to 200 GPa, combining crystal structure predictions with calculations. We predict 15 unique structures, encompassing seven unidentified stoichiometries. Within the S-rich structures, the formation of S atom cages is beneficial for superconductivity, with the superconducting transition temperature 25.86 and 25.30 K for <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:msub><c:mi>LuS</c:mi><c:mn>6</c:mn></c:msub><c:mtext>−</c:mtext><c:mi>C</c:mi><c:mn>2</c:mn><c:mo>/</c:mo><c:mi>m</c:mi></c:mrow></c:math> at 70 GPa and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msub><d:mi>LuS</d:mi><d:mn>6</d:mn></d:msub><d:mtext>−</d:mtext><d:mi>R</d:mi><d:mtext>−</d:mtext><d:mn>3</d:mn><d:mi>m</d:mi></d:mrow></d:math> at 90 GPa, respectively. With the Lu/(Lu+S) ratio increases, the Lu-<e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>d</e:mi></e:math> electrons participate more in the electronic properties at the Fermi energy, resulting in the coexistence of superconductivity and topological nontriviality of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:msub><f:mi>LuS</f:mi><f:mn>2</f:mn></f:msub><f:mtext>−</f:mtext><f:mi>C</f:mi><f:mi>m</f:mi><f:mi>c</f:mi><f:mi>a</f:mi></f:mrow></f:math>, as well as the superconductivity of predicted Lu-rich compounds. Our calculation is helpful for understanding the exotic properties in the transition metal sulfides system under high pressure, providing the possibility of designing alternative superconductors for future experimental and theoretical works.