Interaction-Driven Topological Transitions in Monolayer TaIrTe$_4$

TL;DR

This study combines theory and experiment to explore how interactions and tuning parameters induce various topological phases in monolayer TaIrTe$_4$, revealing a rich phase diagram with potential for novel quantum states.

Contribution

It provides the first comprehensive phase diagram of monolayer TaIrTe$_4$ showing interaction-driven topological transitions using combined theoretical and experimental approaches.

Findings

Identification of multiple topological phases including QSHI and higher-order topological insulators.

Experimental validation of theoretical phase predictions through transport measurements.

Demonstration of tunability of topological states via strain and dielectric screening.

Abstract

Discovering materials that combine topological phenomena with correlated electron behavior is a central pursuit in quantum materials research. Monolayer TaIrTe$_4$ has recently emerged as a promising platform in this context, hosting robust quantum spin Hall insulator (QSHI) phases both within a single-particle gap and within a correlation-induced gap arising from van Hove singularities (vHSs), accessed via electrostatic doping. Its intrinsic monolayer nature offers exceptional tunability and the potential to realize a versatile array of interaction-driven topological phases. In this work, we combine theory and experiment to map the phase landscape of monolayer TaIrTe$_4$. Using Hartree-Fock calculations, we investigate the interaction-driven phase diagram near the vHSs under commensurate filling conditions. By systematically tuning the dielectric screening and strain, we uncover a rich set of ground states--including QSHI, trivial insulator, higher-order topological insulator, and metallic phase--among which are interaction-driven topological phase transitions. Experimentally, we perform both local and nonlocal transport measurements across a broad set of devices, which--due to unavoidable strain variations during fabrication-realize several phases consistent with theoretical predictions. Together, our results lay the groundwork for understanding correlation-driven topological phenomena in TaIrTe$_4$ and open new directions for engineering exotic quantum phases in low-dimensional materials beyond the limitations of moir\'e superlattices.