Abstract
Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy. In particular, strain control over the diverse phase transitions and topological states in two-dimensional transition metal dichalcogenides remains an open challenge. Here, we exploit uniaxial strain to stabilize the long-debated structural ground state of the 2D topological semimetal IrTe2, which is hidden in unstrained samples. Combined angle-resolved photoemission spectroscopy and scanning tunneling microscopy data reveal the strain-stabilized phase has a 6 × 1 periodicity and undergoes a Lifshitz transition, granting unprecedented spectroscopic access to previously inaccessible type-II topological Dirac states that dominate the modified inter-layer hopping. Supported by density functional theory calculations, we show that strain induces an Ir to Te charge transfer resulting in strongly weakened inter-layer Te bonds and a reshaped energetic landscape favoring the 6×1 phase. Our results highlight the potential to exploit strain-engineered properties in layered materials, particularly in the context of tuning inter-layer behavior.
Highlights
Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy
Using external stimuli to manipulate the diverse phenomena observed in quantum materials may allow for tunable control over technologically relevant material properties. Within this context uniaxial strain has recently emerged as a powerful approach to influence the properties of solids[1,2,3,4,5,6] and offers a path to tailor both physical properties and device functionalities, in the 2D transition metal dichalcogides (TMDs)[7,8,9,10]
The family of layered tellurides are promising[12], a prime example of which is 1T-IrTe2. This high-atomic number material is predicted as a type-II bulk-Dirac semimetal with a Dirac point slightly above the Fermi level[13] and presents first-order bulk phase transitions to a 5 × 1 × 5 structure at 280 K, and to an 8 × 1 × 8 structure at 180 K14,15
Summary
Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy. While efforts to control phase transition behavior with strain have focused predominantly on oxide materials, there exist many opportunities within the 2D semimetals, which routinely host multiple nearly degenerate structural, electronic, and topological phases[11], thereby making them sensitive to external perturbation In this regard, the family of layered tellurides are promising[12], a prime example of which is 1T-IrTe2. Charge transfer results in a significant weakening of the majority of interlayer Te bonds in the unit cell, resulting in a tenfold reduction of interlayer hopping in the relevant states, and leaving the bulk-Dirac states as the dominant interlayer transport channel These results demonstrate the power of strain to influence phase transitions, bonding and topology in the layered tellurides, and more broadly in the 2D semimetals
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