Optical-helicity-driven optomagnetic field and photo-spin current in metallic systems*

Interaction among photons, electrons, and spins in condensed matters has opened a research area of opto-spintronics. Circularly polarized photons induce spin density on conduction bands of semiconductors by optical orientation [1, 2], and generate an opto-magnetic field on magnetic moments of insulators by inverse Faraday effect [3, 4]. The observation of optical-helicity-dependent switching of magnetization of metallic ferromagnets has suggested relevant physics in metallic systems [5]. Recently, the opto-magnetic field has been observed in metallic ferromagnets, and its magnitude and direction were explained by interaction energy between angular momentum of photons and magnetization of ferromagnets [6]. For non-magnetic metals, a photo-spin current can occur at interfaces of heavy metals and normal metals due to spin-orbit coupling of heavy metals and inversion symmetry breaking at interfaces [7]. These novel physics enable opto-spintronics in metallic systems with an ultrafast timescale.

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7. G.-M. Choi, D.-G. Lee, S.-W. Lee, K. W. Kim, M. Lim, B.-C. Min, K.-J. Lee, and H.-W. Lee, submitted