Phase Transitions and Electronic Properties in Iridium Tellurides

Iridium tellurides, most notably IrTe₂, are layered transition-metal dichalcogenides that exhibit a rich interplay between lattice, charge and orbital degrees of freedom. On cooling from ambient temperatures, these compounds undergo one or more structural phase transitions, often accompanied by charge-density-wave formation, Ir–Ir dimerisation and modulation of Te–Te interlayer bonds. The resulting distortions reconstruct the Fermi surface, remove van Hove singularities at the Fermi level and give rise to novel electronic states. Spin–orbit coupling in the heavy Ir 5d shell further enriches the phase diagram, stabilising Mott-like dimers and topological Dirac states under strain or reduced dimensionality. Chemical substitution, hydrostatic pressure and thickness control can suppress or tune the charge-ordered ground states, leading in some cases to superconductivity. The sensitivity of IrTe₂ to external stimuli makes it a prototype for studying intertwined electronic orders in low-dimensional quantum materials and offers prospects for strain- and thickness-engineered device applications.

Research from Nature Portfolio

Studies of monolayer IrTe₂ have revealed that reducing the system to a single van der Waals layer stabilises an insulating 2×1 dimer ground state with a large charge-order gap, in contrast to the metallic behaviour of bulk. Angle-resolved photoemission and scanning tunnelling microscopy confirm the absence of interlayer screening, while first-principles calculations attribute the gap opening to cooperative phonon and charge instabilities that lock in local Ir–Ir bonds.

Investigations of IrTe₂ nanoflakes demonstrate that superconductivity can emerge deep inside the stripe charge-ordered phase rather than at its melting point. Thickness-dependent measurements show an enhanced coherence length and electron-pairing strength when the stripe order persists, indicating that inherent fluctuations of the parent state are sufficient to induce a superconducting dome without full suppression of the charge modulation.

Spatially resolved NanoARPES and MicroARPES experiments have mapped electronic inhomogeneity across stripe domains in bulk IrTe₂. Each domain exhibits a distinct two-fold symmetric dispersion with replicated 6×1 superstructure bands, and the disappearance of these features at the transition confirms that the 6×1 modulation directly drives the stripe phase change.

Phase Transitions and Electronic Properties in Iridium Tellurides publication trend

The graph below shows the total number of articles in phase transitions and electronic properties in iridium tellurides across all publications each year (not limited to Nature Index journals).

Technical terms

Charge density wave: Periodic modulation of electronic charge density coupled to a lattice distortion.

Dimerisation: Pairing of two adjacent metal atoms into a bonded unit that lowers symmetry and alters electronic states.

Van der Waals material: Layered solid held together by weak interlayer forces, allowing exfoliation to thin sheets.

Spin–orbit coupling: Interaction between an electron’s spin and its orbital motion around the nucleus, significant in heavy elements.

Van Hove singularity: Divergence in the electronic density of states arising from saddle points in the band structure.

Fermi surface: Surface in momentum space representing occupied electronic states at zero temperature.

References

1. Superconductivity emerging from a stripe charge order in IrTe2 nanoflakes. Nature Communications (2021).
2. The critical role of hot carrier cooling in optically excited structural transitions. npj Computational Materials (2021).
3. Uniaxial strain-induced phase transition in the 2D topological semimetal IrTe2. Communications Materials (2021).
4. First-Principles Theory of Phase Transitions in IrTe2. The Journal of Physical Chemistry Letters (2020).
5. Charge-ordering cascade with spin–orbit Mott dimer states in metallic iridium ditelluride. Nature Communications (2015).
6. Structural phase transition associated with van Hove singularity in 5d transition metal compound IrTe2. New Journal of Physics (2014).
7. Large-gap insulating dimer ground state in monolayer IrTe2. Nature Communications (2022).
8. Spatially-resolved electronic structure of stripe domains in IrTe2 through electronic structure microscopy. Communications Physics (2021).
9. Bonding states underpinning structural transitions in IrTe2 observed with micro-ARPES. Physical Review B (2024).