Theory of ultrafast magnetization of nonmagnetic semiconductors with localized conduction bands

The magnetization of a non-magnetic semiconductor by femtosecond light pulses\nis crucial to achieve an all-optical control of the spin dynamics in materials\nand to develop faster memory devices. However, the conditions for its detection\nare largely unknown. In this work we identify the criteria for the observation\nof ultrafast magnetization and critically discuss the difficulties hindering\nits experimental detection. We show that ultrafast magnetization of a non\nmagnetic semiconductor can be observed in compounds with very localized\nconduction band states and more delocalized valence bands, such as in the case\nof a p-d charge transfer gap. By using constrained and time dependent density\nfunctional theory simulations, we demonstrate that a transient ferrimagnetic\nstate can be induced in diamagnetic semiconductor V2O5 via ultrafast pulses at\nrealistic fluences. The ferrimagnetic state has opposite magnetic moments on\nvanadium (conduction) and oxygen (valence) states. Our methodology outruns the\ncase of V2O5 as it identifies the key requirements for a computational\nscreening of ultrafast magnetism in non-magnetic semiconductors.\n