2 research outputs found
Unveiling the orbital-selective electronic band reconstruction through the structural phase transition in TaTe
Tantalum ditelluride TaTe 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 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 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 states, namely
the 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.Comment: 21 pages, 5 figure
Ultrafast Control of Crystal Structure in a Topological Charge-Density-Wave Material
Optical control of crystal structures is a promising route to change physical
properties including topological nature of a targeting material. Time-resolved
X-ray diffraction measurements using the X-ray free-electron laser are
performed to study the ultrafast lattice dynamics of VTe, which shows a
unique charge-density-wave (CDW) ordering coupled to the topological surface
states as a first-order phase transition. A significant oscillation of the CDW
amplitude mode is observed at a superlattice reflection as well as Bragg
reflections. The frequency of the oscillation is independent of the fluence of
the pumping laser, which is prominent to the CDW ordering of the first-order
phase transition. Furthermore, the timescale of the photoinduced
1 to 1 phase transition is independent of the period of
the CDW amplitude mode