Continuous Strain Modulation of Moiré Superlattice Symmetry From Triangle to Rectangle.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Moiré superlattices in van der Waals (vdW) bilayers offer tunable platforms for novel physics, including correlated electronic states and moiré excitons.
• Current limitations include fixed crystal symmetry, hindering exploration of symmetry-dependent phenomena.

Purpose of the Study:

• To develop a straightforward method for controlling and modulating the symmetry of moiré superlattices.
• To enable new tuning knobs for moiré quantum matter by deforming superlattice symmetry.

Main Methods:

• Utilizing vdW heterostructures on flexible substrates to introduce uniaxial strain via substrate bending.
• Employing numerical calculations to design specific strain conditions for symmetry deformation.
• Visualizing real-space moiré superlattice deformation using piezoresponse force microscopy.

Main Results:

• A room-temperature, ambient method for controlling moiré superlattice symmetry was successfully demonstrated.
• The moiré superlattice was continuously deformed from triangular to rectangular symmetry using uniaxial strain.
• Band calculations confirmed the persistence of nearly flat moiré minibands in the rectangular lattice structure.

Conclusions:

• The developed strain-based method provides a versatile tool for tuning moiré superlattice symmetry.
• This technique opens new avenues for investigating symmetry-dependent electronic properties in moiré quantum matter.
• The ability to control symmetry complements existing tuning parameters like lattice constant and electric fields.