Weyl Semimetal Phase in Solid-Solution Narrow-Gap Semiconductors

We theoretically investigate ferromagnetic ordering in magnetically doped solid-solution narrow-gap semiconductors with the strong spin-orbit interaction such as Cr-doped Bi-2(SexTe1-x)(3). We compute the spontaneous magnetization of impurities and itinerant electrons, and estimate the critical temperature as a function of the concentration of magnetic dopants and the strength of the spin-orbit interaction. It is found that the critical temperature is proportional to the concentration of dopants and enhanced with the strong spin-orbit interaction. It is also found that the ferromagnetic transition could make the system turn to the Weyl semimetal which possesses a pair of Weyl points separating in the momentum space.