Electronic states in superconducting type-II Dirac semimetal: 1T-PdSeTe

We have investigated the surface and bulk electronic structures of the superconducting type-II Dirac semimetal 1T-PdSeTe. The superconducting transition temperature <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>T</a:mi><a:mtext>c</a:mtext></a:msub><a:mo>=</a:mo><a:mn>3.2</a:mn></a:mrow></a:math> K was almost twice as high as <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msub><b:mi>T</b:mi><b:mtext>c</b:mtext></b:msub><b:mo>=</b:mo><b:mn>1.6</b:mn></b:mrow></b:math> K in 1T-<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:msub><c:mi>PdTe</c:mi><c:mn>2</c:mn></c:msub></c:math>. Scanning transmission electron microscopy measurements showed homogeneously mixed Se and Te atoms in the chalcogen layers, consistent with the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:msub><d:mi>CdI</d:mi><d:mn>2</d:mn></d:msub></d:math>-type crystal structure. Angle-resolved photoemission spectroscopy measurements and density functional theory calculations indicated the existence of the topological surface states, and the overall band structures were similar to those of 1T-<e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:msub><e:mi>PdTe</e:mi><e:mn>2</e:mn></e:msub></e:math>. These results suggest that the <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:msub><f:mi>CdI</f:mi><f:mn>2</f:mn></f:msub></f:math>-type lattice symmetry dictates the band dispersion, regardless of atomic disorder in the chalcogen layers. As the electronic band dispersion and the local structures were persistent upon substitution, the enhancement of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:msub><g:mi>T</g:mi><g:mtext>c</g:mtext></g:msub></g:math> is likely associated with the chemical pressure. Our results provide insight into the effects of the solid solution on the surface and bulk electronic states as well as the superconducting transition temperature.