Unveiling the orbital-selective electronic band reconstruction through the structural phase transition in TaTe2

Tantalum ditelluride (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>TaTe</a:mi><a:mn>2</a:mn></a:msub></a:math>) belongs to the family of layered transition metal dichalcogenides but exhibits a unique structural phase transition at around 170 K that accompanies the rearrangement of the Ta atomic network from a “ribbon chain” to a “butterfly-like” pattern. While multiple mechanisms including Fermi surface nesting and chemical bonding instabilities have been intensively discussed, the origin of this transition remains elusive. Here we investigate the electronic structure of single-crystalline <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msub><b:mi>TaTe</b:mi><b:mn>2</b:mn></b:msub></b:math> with a particular focus on its modifications through the phase transition, by employing core-level and angle-resolved photoemission spectroscopy combined with first-principles calculations. Temperature-dependent core-level spectroscopy demonstrates a splitting of the Ta <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mn>4</c:mn><c:mi>f</c:mi></c:mrow></c:math> core-level spectra through the phase transition indicative of the Ta-dominated electronic state reconstruction. Low-energy electronic state measurements further reveal an unusual kink-like band reconstruction occurring at the Brillouin zone boundary, which cannot be explained by Fermi surface nesting or band-folding effects. On the basis of the orbital-projected band calculations, this band reconstruction is mainly attributed to the modifications of specific Ta <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mn>5</d:mn><d:mi>d</d:mi></d:mrow></d:math> states, namely, the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:msub><e:mi>d</e:mi><e:mrow><e:mi>X</e:mi><e:mi>Y</e:mi></e:mrow></e:msub></e:math> orbitals (the ones elongating along the ribbon chains) at the center Ta sites of the ribbon chains. The present results highlight the strong orbital-dependent electronic state reconstruction through the phase transition in this system and provide fundamental insights towards understanding complex electron-lattice-bond coupled phenomena. Published by the American Physical Society 2024