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Nat Mater. 2013 Mar;12(3):207-11. doi: 10.1038/nmat3505. Epub 2012 Dec 2.

Tightly bound trions in monolayer MoS2.

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1
Departments of Physics and Electrical Engineering, Columbia University, New York, NY 10027, USA.

Abstract

Two-dimensional (2D) atomic crystals, such as graphene and transition-metal dichalcogenides, have emerged as a new class of materials with remarkable physical properties. In contrast to graphene, monolayer MoS(2) is a non-centrosymmetric material with a direct energy gap. Strong photoluminescence, a current on/off ratio exceeding 10(8) in field-effect transistors, and efficient valley and spin control by optical helicity have recently been demonstrated in this material. Here we report the spectroscopic identification in a monolayer MoS(2) field-effect transistor of tightly bound negative trions, a quasiparticle composed of two electrons and a hole. These quasiparticles, which can be optically created with valley and spin polarized holes, have no analogue in conventional semiconductors. They also possess a large binding energy (~ 20 meV), rendering them significant even at room temperature. Our results open up possibilities both for fundamental studies of many-body interactions and for optoelectronic and valleytronic applications in 2D atomic crystals.

PMID:
23202371
DOI:
10.1038/nmat3505
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