A Novel × Superstructure in Epitaxially Grown 1T-TaTe₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• 2D Materials

Background:

• Spontaneous electronic orders are key to complex quantum states and heterostructures in 2D materials.
• 1T-TaTe2 is a transition metal dichalcogenide with potential for novel electronic properties.

Purpose of the Study:

• To report the realization of a novel $\sqrt{7}$ × $\sqrt{7}$ charge order in few-layer 1T-TaTe2 films.
• To investigate the stabilization of different charge density wave orders in 1T-TaTe2.
• To understand the persistence of these orders in thicker films.

Main Methods:

• Molecular beam epitaxy for growing few-layer 1T-TaTe2 films.
• Photoemission spectroscopy to probe electronic states.
• Scanning probe microscopy to characterize surface structure and charge order.
• Post-growth annealing at controlled temperatures.

Main Results:

• Monolayer 1T-TaTe2 exhibits metastable charge density wave orders, including the $\sqrt{7}$ × $\sqrt{7}$ superstructure.
• The $\sqrt{7}$ × $\sqrt{7}$ order can be selectively stabilized by annealing temperature.
• This $\sqrt{7}$ × $\sqrt{7}$ order persists in 1T-TaTe2 films up to 8 layers thick.

Conclusions:

• A previously unrealized $\sqrt{7}$ × $\sqrt{7}$ electronic order has been identified in 1T-TaTe2.
• Epitaxial growth and annealing provide a route to control this novel electronic order.
• The findings advance the understanding of electronic orders in transition metal dichalcogenides and heterostructure engineering.