Optical vortex probe of loop-current chirality in moiré materials

Abstract

We propose a symmetry-resolved optical probe of intrinsic loop-current chirality in moiré materials, with twisted bilayer graphene as a representative realization. Interlayer interference generates chiral electronic circulation on triangular plaquettes, giving rise to an intrinsic geometric chirality that enters the second-order response through a $C_3$-selected angular harmonic of the Berry curvature and can be isolated by the orbital-angular-momentum difference $\Delta \ell$ of interfering optical vortex beams. When moiré $C_3$ symmetry is preserved, the intrinsic contribution appears in the $\Delta \ell =3$ channel of the helicity-dependent dc photocurrent, whereas $C_3$-breaking perturbations activate additional channels. These results establish angular-momentum-resolved nonlinear optics as a route to probing geometric chirality in moiré and other symmetry-engineered quantum materials.

8 pages, 1 figure

References in corpus (8)

• Lattice relaxation and energy band modulation in twisted bilayer graphenes
• Non-linear electromagnetic response of graphene
• Continuum models for twisted bilayer graphene: the effects of lattice deformation and hopping parameter
• Tunable Layer Circular Photogalvanic Effect in Twisted Bilayers
• Nano-imaging photoresponse in a moiré unit cell
• Nano-photocurrent mapping of local electronic structure in twisted bilayer graphene
• Twisted-light-induced optical transitions in semiconductors: Free-carrier quantum kinetics
• Description of molecular chirality and its analysis with high harmonic generation