Valley Polarization of Trions and Magnetoresistance in Heterostructures of MoS2 and Yttrium Iron Garnet.
ACS Nano
; 11(12): 12257-12265, 2017 12 26.
Article
in En
| MEDLINE
| ID: mdl-29182851
Manipulation of spin degree of freedom (DOF) of electrons is the fundamental aspect of spintronic and valleytronic devices. Two-dimensional transition metal dichalcogenides (2D TMDCs) exhibit an emerging valley pseudospin, in which spin-up (-down) electrons are distributed in a +K (-K) valley. This valley polarization gives a DOF for spintronic and valleytronic devices. Recently, magnetic exchange interactions between graphene and magnetic insulator yttrium iron garnet (YIG) have been exploited. However, the physics of 2D TMDCs with YIG have not been shown before. Here we demonstrate strong many-body effects in a heterostructure geometry comprising a MoS2 monolayer and YIG. High-order trions are directly identified by mapping absorption and photoluminescence at 12 K. The electron doping density is up to â¼1013 cm-2, resulting in a large splitting of â¼40 meV between trions and excitons. The trions exhibit a high circular polarization of â¼80% under optical pumping by circularly polarized light at â¼1.96 eV; it is confirmed experimentally that both phonon scattering and electron-hole exchange interaction contribute to the valley depolarization with temperature; importantly, a magnetoresistance (MR) behavior in the MoS2 monolayer was observed, and a giant MR ratio of â¼30% is achieved, which is 1 order of magnitude larger than the reported ratio in MoS2/CoFe2O4 heterostructures. Our experimental results confirm that the giant MR behaviors are attributed to the interfacial spin accumulation due to YIG substrates. Our work provides an insight into spin manipulation in a heterostructure of monolayer materials and magnetic substrates.
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01-internacional
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MEDLINE
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En
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ACS Nano
Year:
2017
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Article
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