18533
For example , Dirac valley polarization has been demonstrated in mechanically exfoliated monolayer MoS2 samples by polarization - resolved photoluminescence , although polarization has rarely been seen at room temperature .
 Chemical: MoS2
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: MoS2