Shintaro Takayoshi, Hideo Aoki, Takashi Oka
We theoretically predict a non-equilibrium phase transition in quantum spin systems induced by laser, which provides a purely quantum-mechanical way for a coherent control of magnetization. Namely, when a circularly polarized laser is applied to a spin system, the magnetic component of laser induces a magnetization normal to the plane of polarization, leading to an ultrafast phase transition. We first demonstrate this numerically for an S=1 antiferromagnetic Heisenberg spin chain, where the topologically-ordered Haldane state gives way to a new state with an emerging magnetization. We then elucidate its physical mechanism by applying a many-body Floquet picture. The theory also indicates that the phenomenon should occur in general quantum spin systems with a magnetic anisotropy. The required laser frequency is in the THz range, and the intensity within a prospective experimental feasibility.
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http://arxiv.org/abs/1302.4460
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