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Second harmonic spectroscopy to optically detect valley polarization in

TitleSecond harmonic spectroscopy to optically detect valley polarization in
Publication TypeJournal Article
Year of Publication2017
AuthorsHipolito, F., and Pereira Vitor M.
Journal2D Mater.
Date Published06/2017
Keywords2D materials, bilayer graphene, generation, molybdenum-disulfide, MoS2, second harmonic generation, Semiconductors, valley polarization

Valley polarization (VP), an induced imbalance in the populations of a multi-valley electronic system, allows emission of second harmonic (SH) light even in centrosymmetric crystals such as graphene. Whereas in systems such as MoS2 or BN this adds to their intrinsic quadratic response, SH generation in a multi-valley inversion-symmetric crystal can provide a direct measure of valley polarization. By computing the nonlinear response and characterizing theoretically the respective SH as a function of polarization, temperature, electron density, and degree of VP, we demonstrate the possibility of disentangling and individually quantifying the intrinsic and valley contributions to the SH. A specific experimental setup is proposed to obtain direct quantitative information about the degree of VP and allow its remote mapping. This approach could prove useful for direct, contactless, real-space monitoring of valley injection and other applications of valley transport and valleytronics.


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