Observation of a uniaxial strain-induced phase transition in the 2D topological semimetal IrTe$_2$

TL;DR

This study demonstrates how uniaxial strain can induce a phase transition in the 2D topological semimetal IrTe$_2$, revealing new topological states and structural phases through combined experimental and theoretical analysis.

Contribution

The paper provides the first experimental evidence that uniaxial strain stabilizes a hidden 6x1 phase in IrTe$_2$, enabling control over its topological and structural properties.

Findings

Strain stabilizes a 6x1 phase with a Lifshitz transition.

Strain induces charge transfer weakening inter-layer bonds.

Strain enables access to type-II topological Dirac states.

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 (2D) transition metal dichalcogenides (TMDs) remains an open challenge. Here, we exploit uniaxial strain to stabilize the long-debated structural ground state of the 2D topological semimetal IrTe$_2$, which is hidden in unstrained samples. Combined angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) data reveal the strain-stabilized phase has a 6x1 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 (DFT) calculations, we show that strain induces a charge transfer strongly weakening the inter-layer Te bonds and thus reshaping the energetic landscape of the system in favor of the 6x1 phase. Our results highlight the potential to exploit strain-engineered properties in layered materials, particularly in the context of tuning inter-layer behavior.