Strain Tunable Semimetal-Topological-Insulator Transition in Monolayer 1T^{'}-WTe_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Materials

Background:

• Quantum spin Hall insulators exhibit conducting edge channels due to nontrivial bulk topology.
• Monolayer 1T^{'}-WTe_{2} shows quantized edge conductance but has a limited coherence length (approx. 100 nm) due to its semimetallic nature.

Purpose of the Study:

• To overcome the coherence length limitation in monolayer 1T^{'}-WTe_{2}.
• To engineer the electronic structure of 1T^{'}-WTe_{2} to achieve a full gap insulating phase.

Main Methods:

• Strain engineering (compressive along a-axis or tensile along b-axis).
• Molecular beam epitaxy (MBE).
• In situ scanning tunneling microscopy/spectroscopy (STM/STS).

Main Results:

• Compressive or tensile strain successfully drives 1T^{'}-WTe_{2} into a full gap insulating phase.
• MBE and in situ STM/STS confirmed the strain-induced phase transition.
• Topological edge states demonstrate robustness under applied strain.

Conclusions:

• Strain engineering is an effective method to achieve a topological insulating phase in monolayer 1T^{'}-WTe_{2}.
• This approach enhances the coherence length and preserves the topological properties of edge states.
• The findings pave the way for practical applications of topological insulators.