Optical signatures of periodic magnetization: the moiré Zeeman effect

Abstract

Detecting magnetic order at the nanoscale is of central interest for the study of quantum magnetism in general, and the emerging field of moiré magnets in particular. Here, we analyze the exciton band structure that arises from a periodic modulation of the valley Zeeman effect. Despite long-range electron-hole exchange interactions, we find a sizable splitting in the energy of the bright circularly-polarized exciton Umklapp resonances, which serves as a direct optical probe of magnetic order. We first analyze quantum moiré magnets realized by periodic ordering of electron spins in Mott-Wigner states of transition metal dichalcogenide (TMD) monolayers or twisted bilayers: we show that spin-valley dependent exciton-electron interactions allow for probing the spin-valley order of electrons and demonstrate that it is possible to observe unique signatures of ferromagnetic order in a triangular lattice and both ferromagnetic and Néel order in a honeycomb lattice. We then focus on semiclassical moiré magnets realized in twisted bilayers of ferromagnetic materials: we propose a detection scheme for moiré magnetism which is based on inter-layer exchange coupling between spins in a moiré magnet and excitons in a TMD monolayer.

6+5 pages, 4+3 figures, 1 table

References in corpus (4)

• Resonantly hybridised excitons in moiré superlattices in van der Waals heterostructures
• Valley Zeeman Effect in Elementary Optical Excitations of a Monolayer WSe2
• Valley Splitting and Polarization by the Zeeman Effect in Monolayer MoSe2
• Layer-Resolved Magnetic Proximity Effect in van der Waals Heterostructures

Cited by in corpus (2)

• Kagome chiral spin liquid in transition metal dichalcogenide moiré bilayers
• Mott-moiré excitons