Intelligent infrared sensing enabled by tunable moiré quantum geometry.

Area of Science:

• Condensed matter physics
• Quantum geometry
• Nonlinear optics

Background:

• Quantum geometric properties like Berry curvature influence electron behavior in solids.
• The bulk photovoltaic effect (BPVE) is a nonlinear optical phenomenon governed by quantum geometry.
• Infrared BPVE has not been observed in graphene or moiré systems previously.

Purpose of the Study:

• To observe and characterize tunable mid-infrared BPVE in twisted double bilayer graphene (TDBG).
• To investigate the role of moiré-induced symmetry breaking and quantum geometry in nonlinear light-matter interactions.
• To demonstrate a novel sensing platform for polarimetry and wavelength detection.

Main Methods:

• Fabrication and characterization of twisted double bilayer graphene (TDBG) devices.
• Measurement of mid-infrared photoresponse at 5 µm and 7.7 µm.
• Application of convolutional neural networks for simultaneous full-Stokes polarimetry and wavelength detection.

Main Results:

• Observation of tunable mid-infrared BPVE in TDBG, tunable by external electric fields.
• Photoresponse demonstrated strong dependence on excitation light polarization.
• A single TDBG device with a 3x3 µm² footprint achieved simultaneous polarimetry and wavelength detection.

Conclusions:

• Moiré-engineered quantum geometry plays a crucial role in tunable nonlinear light-matter interactions.
• TDBG offers a promising platform for exploring quantum geometric effects in nonlinear optics.
• The developed device provides a pathway for compact, on-chip intelligent sensing technologies.