Article open access publication

Second harmonic spectroscopy to optically detect valley polarization in 2D materials

2D Materials, IOP Publishing, ISSN 2053-1583

Volume 4, 2, 2017

DOI:10.1088/2053-1583/aa6f4d, Dimensions: pub.1085190064,


Hipolito, F (1) (2)



  1. (1) Aalborg University, grid.5117.2, AAU
  2. (2) National University of Singapore, grid.4280.e








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 MoS 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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