Probing picometre-scale interlayer deformations via hyperbolic polaritons

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Van der Waals (vdW) materials offer tunable properties via strain engineering.
• Characterizing out-of-plane strain at the picometer scale, especially at interfaces, is challenging.
• Existing methods struggle with non-invasive, quantitative analysis of subtle deformations.

Purpose of the Study:

• To develop a novel, non-invasive optical method for detecting picometer-scale out-of-plane strain in vdW materials.
• To enable quantitative characterization of interlayer deformations at buried interfaces.
• To bridge nanomechanics and photonics for precise stress landscape visualization.

Main Methods:

• Utilizing mid-infrared out-of-plane hyperbolic polaritons (oHPs) in hexagonal boron nitride (hBN).
• Exploiting the strain-induced softening of 'dark' out-of-plane transverse optical (oTO) phonons activated by oHPs.
• Achieving atomic displacement sensitivity of approximately 10 pm.

Main Results:

• Demonstrated a polaritonic optical method for picometer-scale out-of-plane strain detection.
• Successfully measured interlayer deformations in planar hBN and hBN-based heterostructures.
• Validated the technique's ability to detect ultradeep-subwavelength mechanical deformations.

Conclusions:

• The polariton-based picometrology method provides unprecedented sensitivity to interlayer strain.
• This technique offers a non-destructive way to map hidden stress landscapes with atomic precision.
• The approach advances the study of mechanical properties in vdW materials and heterostructures.