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Light-induced ferromagnetism in moiré superlattices
Xi Wang1,2, Chengxin Xiao3,4, Heonjoon Park1
1Department of Physics, University of Washington, Seattle, WA, USA.
Nature
|April 21, 2022
Summary
Optical excitation can tune spin interactions in moiré superlattices, inducing ferromagnetism. This discovery in WS2/WSe2 moiré systems offers new control over quantum materials.
Area of Science:
- Condensed Matter Physics
- Quantum Materials Science
- Materials Engineering
Background:
- Many-body interactions are fundamental to correlated physics and controlling electronic phases.
- Two-dimensional moiré superlattices offer a tunable platform for quantum engineering complex phenomena.
- Tuning parameters include twist angle, electric field, carrier filling, and interlayer coupling.
Purpose of the Study:
- To investigate the effect of optical excitation on spin-spin interactions in moiré superlattices.
- To explore the potential for inducing and controlling magnetic order via optical means.
- To understand the mechanism of exciton-mediated spin interactions in WS2/WSe2 moiré systems.
Main Methods:
- Utilized WS2/WSe2 moiré superlattices.
- Employed optical excitation at exciton resonance.
- Measured magnetic properties using reflective magnetic circular dichroism (RMCD) as a function of magnetic field and excitation power.
Main Results:
- Observed the emergence of ferromagnetic order in WS2/WSe2 moiré superlattices under optical excitation.
- A hysteresis loop in RMCD, indicative of ferromagnetism, appeared near -1/3 filling factor and persisted to charge neutrality.
- The observed magnetic order is mediated by itinerant photoexcited excitons, enabling long-range interactions even in dilute hole regimes.
Conclusions:
- Optical excitation provides a dynamic tuning knob for manipulating spin-spin interactions in moiré quantum matter.
- Exciton-mediated exchange coupling offers a novel pathway to achieve magnetic order in 2D materials.
- This work opens new avenues for controlling and engineering the magnetic properties of moiré superlattices.
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