Dual quantum spin Hall insulator by density-tuned correlations in TaIrTe₄

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• The study of quantum states of matter is advanced by combining topology and electron correlations.
• Introducing electron correlations to quantum spin Hall (QSH) insulators can yield exotic topological orders, such as fractional topological insulators.
• These phenomena are not observed in quantum Hall and Chern insulator systems.

Purpose of the Study:

• To report the discovery of a new dual QSH insulator in monolayer TaIrTe₄.
• To investigate the interplay between single-particle topology and electron correlations in TaIrTe₄.
• To explore the emergence of topological states in correlated insulating phases.

Main Methods:

• Experimental synthesis and characterization of intrinsic monolayer TaIrTe₄.
• Transport measurements to probe QSH insulator properties, including nonlocal transport and edge conductance.
• Tuning electron density to induce correlations and investigate phase transitions.

Main Results:

• Monolayer TaIrTe₄ exhibits QSH insulator behavior at charge neutrality with quantized helical edge conductance.
• An unexpected insulating state emerges upon electron doping, potentially due to a charge density wave (CDW) driven by van Hove singularities.
• The QSH state is surprisingly restored within the CDW-induced insulating gap.

Conclusions:

• Monolayer TaIrTe₄ serves as a novel dual QSH insulator, demonstrating the coexistence of topological order and CDW.
• The findings bridge the physics of spin and charge orders, offering insights into correlated topological states.
• This discovery provides a new platform for exploring time-reversal-symmetric fractional phases and novel electromagnetic phenomena through CDW superlattices.