Theory of ultrafast magnetization of non-magnetic semiconductors with localized conduction bands

TL;DR

This paper identifies conditions under which ultrafast magnetization can be observed in non-magnetic semiconductors, demonstrating through simulations that transient ferrimagnetic states can be induced with femtosecond pulses.

Contribution

It provides criteria for detecting ultrafast magnetization and introduces a computational approach to screen non-magnetic semiconductors for ultrafast magnetic responses.

Findings

Ultrafast magnetization occurs in compounds with localized conduction and delocalized valence bands.

Transient ferrimagnetic states can be induced in V2O5 using femtosecond pulses.

The methodology helps identify key requirements for ultrafast magnetism in non-magnetic semiconductors.

Abstract

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