PerspectiveApplied Physics

Electronic Control of Circularly Polarized Light Emission

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Science  16 May 2014:
Vol. 344, Issue 6185, pp. 702-703
DOI: 10.1126/science.1254496

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Circularly polarized (CP) light has many applications, including circular dichroism spectroscopy (to determine the secondary structure of proteins), three-dimensional (3D) displays, spintronics, and even quantum computation. However, CP light is usually created with optical filters, and changing the handedness (left or right) of the polarization requires mechanical rotation of the filters. Alternatively, chiral organic lightemitting diodes with a fixed circular polarization or spin light-emitting diodes, which require an external magnetic field, could be used. On page 725 of this issue, Zhang et al. (1) demonstrate CP electroluminescence from monolayers and multilayers of tungsten diselenide (WSe2) and other transition metal dichalcogenides (TMDs). The handedness of the CP light is directly controlled by the direction of the in-plane electric field. This effect is not only interesting for applications, but also reveals the “valley” properties of the electronic bands of 2D TMDs.