Optical evidence for bonding-antibonding splitting inIrTe2

Ultrafast dissolution and creation of bonds in IrTe 2 induced by photodoping

“…This is a rather intriguing result and illustrates complex light-induced chemistry driven by ultrafast changes in the occupation of antibonding and bonding d orbitals. This electronic temperature range (3 × 10 3 to 2 × 10 4 K) also coincides with the width of the d xy antibonding band predicted in ( 13 , 17 ).…”

“…IrTe 2 is a quasi–two-dimensional layered system, which undergoes a first-order structural transition between two crystalline phases at 260 K ( 12 ). The conduction electron density becomes modulated in a complex way, and modifying forces among the ions and generating PLDs with the bond lengths shortened: Ir-Ir and Te-Te bond lengths in the low-temperature (LT) phase decrease by 20 and 10%, respectively, compared with those in the high-temperature (HT) phase ( 13 – 17 ). This is due to bond formations, observed as the formation of in-plane Ir dimers and/or polymerization of Te chains ( 12 , 13 , 15 ) and accompanied by orbital/charge ordering observed by core-level photoemission spectroscopy ( 18 , 19 ).…”

“…According to angle-resolved photoemission spectroscopy and density functional theory (DFT) studies ( 13 , 16 ), the electronic structure of IrTe 2 near the Fermi level ( E F ) shows a multi-orbital system consisting of Ir 5d and Te 5p and preserves its metallic properties in both LT and HT phases. In the LT phase, the density of states (DOS) at the bottom of the conduction band has a large contribution from Ir t 2g orbitals, and the d xy orbital is expected to play an important role in the structural phase transition and stabilization of the LT phase ( 13 , 17 ). Dimerization in IrTe 2 is quite a special example among phase transitions exhibited in transition metal dichalcogenides, in contrast to the well-known charge density wave (CDW) type transition, resulting in an energy gap formation at E F in many other transition metal dichalcogenides and rare earth tellurides ( 20 – 22 ).…”

Surface phases of the transition-metal dichalcogenide IrTe2

“…The stacking sequence of the striped phase has the same periodicity along both the c-axis direction and a-axis directions (5×1×5). As stated previously, this is unexpected for a weakly bounded layered material [23][24][25]. Such ordering turns the high-temperature trigonal phase into the lowtemperature triclinic phase, with new unit cell vectors orientated in entirely different directions (the new c-axis is not perpendicular to a and b) [6,[26][27][28].…”

Microscopic force driving the photoinduced ultrafast phase transition: Time-dependent density functional theory simulations of IrTe2

“…However, recent experimental and theoretical works also illustrate that it is the Te p orbital, rather than the CDW, playing the main role in causing a local bonding instability in the observed structural phase transition [17,20,21]. The d xy orbital of the Ir-Ir dimers is also suggested to play a dominant role in the structural phase transition [14,16,22,23]. An interplay among the charge-density-wave-like lattice modulation, in-plane dimer ordering, and the uniform lattice deformation is also postulated as the origin of phase transition [16].…”