Unveiling the orbital-selective electronic band reconstruction through the structural phase transition in TaTe_2
arXiv (Cornell University)(2023)
摘要
Tantalum ditelluride TaTe_2 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 TaTe_2 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 4f 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 5d states, namely
the d_XY 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.
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关键词
structural phase transition,orbital-selective
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