The Moire pattern is observed in 2D semiconductors like transitional metal dichalcogenides when two layers are placed one above another with a slight difference in the angle. Basically, a pattern observed when two patterns must not be completely identical, but rather displaced, rotated So, in this experiment, they had used two different TMDCs, i.e, MoSe2&WSe2(transition metal dichalcogenides). So their band structures are different also having type -2 band alignment. So, from the below picture, we can see a moire pattern such that, it has 3fold rotational symmetry. So, in the potential diagram, we will see associated potential variations.
The optical properties of a semiconductor are determined by their band gap and generation of excitons. Scientists found that at low temperature (around 1.6K, also vanishes above 30K), the excitons are getting trapped in the moire potential wells. The concept of potential well is obtained from the several narrow peaks in the absorption spectrum at low temperature. When we increase the power of the laser, then the potential well fills and the narrow peaks disappear.
The main property of moire excitons is they have valley polarization. i.e., we can selectively populate electrons in k+ and k- points in Brillouin zone by applying right circularly or left circularly polarized light, Because, When they measured the g-factor of excitons at different magnetic fields, they found almost same g-factor. It is the symbol of valley pairing of the excitons in moire pattern. This pairing can be varying by varying the orientation of layers. So, moire excitons are very useful in valleytronics, which helps us to write and read data.
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