Observation of the Time-Reversal Symmetric Hall Effect in Graphene–WSe₂ Heterostructures at Room Temperature

Abstract

In this Letter, we provide experimental evidence of the time-reversal symmetric Hall effect in a mesoscopic system, namely, high-mobility graphene–WSe2 heterostructures. This linear, dissipative Hall effect, whose sign depends on the sign of the charge carriers, persists up to room temperature. The magnitude and the sign of the Hall signal can be tuned using an external perpendicular electric field. Our joint experimental and theoretical study establishes that the strain induced by lattice mismatch, or alignment angle inhomogeneity, produces anisotropic bands in graphene while simultaneously breaking the inversion symmetry. The band anisotropy and reduced spatial symmetry lead to the appearance of a time-reversal symmetric Hall effect. Our study establishes graphene–transition metal dichalcogenide-based heterostructures as an excellent platform for studying the effects of broken symmetry on the physical properties of band-engineered two-dimensional systems.

Roses in the nonperturbative current response of artificial crystals

“…Finally, we note that most moiré systems display some degree of heterostrain which breaks rotation symmetry ( 40 ). In some cases, this feature is necessary to observe a second-order Hall effect ( 36 – 39 ). Hence, in the presence of strain, the symmetry of the rose pattern at low fields is expected to be reduced, while at larger fields, the petal structure enforced by symmetry is expected to be only slightly perturbed.…”

“…TDBG consists of a stack of two (AB or BA) Bernal bilayer graphene layers that are twisted relative to each other ( 11 , 35 ). A second-order Hall effect was recently observed in TDBG for twist angles where was broken by strain ( 36 – 39 ), making this system a promising platform for studying nonperturbative responses. For such small twists, one can again use a valley-projected theory; see SI Appendix , section IV .…”

Controlling Umklapp Scattering in a Bilayer Graphene Moiré Superlattice

“…High-quality hBN/BLG/hBN heterostructures were fabricated using the dry transfer technique (section S1 of the Supporting Information). − The top hBN was aligned at nearly 0° with BLG, and the bottom hBN was intentionally misaligned to a large angle to ensure that a moiré pattern forms only between top hBN and BLG (Figure a). The device is in a hall bar geometry (Figure b) with dual gates to tune carrier density n and vertical displacement field D independently via the equations n = ( C tg V tg + C bg V bg )/ e + n r and D = ( C tg V tg – C bg V bg )/2 + D r , respectively.…”