# Difference between graphics in the Zeeman effect

I've been reading articles about Zeeman's effect on TMDs specifically on WSe$$_2$$. In the article: Srivastava, Ajit, Sidler, Meinrad, Allain, Adrien, Lembke, Dominik, Kis, Andras, Imamoğlu, A., Valley Zeeman effect in elementary optical excitations of monolayer WSe$$_2$$. Nature Physics, 11:141-147, 2015 in the first two curves, the blue curve representing the K valley is shifted to the higher energy region while the red curve representing the K' valley is shifted to the lower energy region.

However, in an article on the same topic: Aivazian, G., Zhirui, Gong, Jones, Aaron, Chu, Rui-Lin, Yan, J., Mandrus, D., Zhang, Chuanwei, Cobden, David, Yao, Wang, Xu, X., Magnetic control of valley pseudospin in monolayer WSe$$_2$$. Nature Physics, 11:148-152, 2015 the red line is in the region of higher energy while the blue line is in the region of lower energy.

Are the two articles not contradicting each other as it is the same material (WSe$$_2$$) and the applied magnetic field is positive? Which of the two representations is right?

• Not an expert on this, but could it be due to a difference in labeling? In the figure from the first paper, the K valley has a spin up electron that is excited by left circularly polarized light. In the corresponding figure in the second paper, the K valley has a down spin electron excited with right circularly polarized light.
– Tyberius
Jul 15 at 3:14
• @Tyberius Yes, you are right that the spins are exchanged on both articles. But if they are the same material in the same valleys shouldn't they have the same spins? In the first image they also use $\sigma^+$ to designate clockwise, whereas $\sigma^+$ is usually used to designate counterclockwise. But thanks for your reminder. I hadn't really noticed the spins Jul 15 at 11:15