Spin Radiation of Electrons, Excitons, and Phonons
Abstract: In the celebrated Stern-Gerlach experiment an inhomogeneous static magnetic field separates a beam of charge-neutral atoms with opposite spins, thereby driving a ``spin current" normal to the propagation direction. Here we generalize it to the dynamic scenario by demonstrating a spin transfer between an AC inhomogeneous magnetic field and intraband electrons or charge-neutral excitons and phonons. We predict that parametric pumping can efficiently radiate their DC spin currents from local AC magnetic sources with van der Waals semiconductors as prototypes. This mechanism brings a unified and efficient paradigm in the spin transport of distinct mobile carriers.
- The local optical field can be equivalently expressed in the form 𝐡(𝝆,t)=∑𝐪(𝐇*(−𝐪)eiωt+𝐇(𝐪)e−iωt)ei𝐪⋅𝝆𝐡𝝆𝑡subscript𝐪superscript𝐇𝐪superscript𝑒𝑖𝜔𝑡𝐇𝐪superscript𝑒𝑖𝜔𝑡superscript𝑒⋅𝑖𝐪𝝆\mathbf{h}({\boldsymbol{\rho}},t)=\sum_{\mathbf{q}}\left(\mathbf{H}^{*}(% \mathbf{-q})e^{i\omega t}+\mathbf{H}(\mathbf{q})e^{-i\omega t}\right)e^{i% \mathbf{q}\cdot{\boldsymbol{\rho}}}bold_h ( bold_italic_ρ , italic_t ) = ∑ start_POSTSUBSCRIPT bold_q end_POSTSUBSCRIPT ( bold_H start_POSTSUPERSCRIPT * end_POSTSUPERSCRIPT ( - bold_q ) italic_e start_POSTSUPERSCRIPT italic_i italic_ω italic_t end_POSTSUPERSCRIPT + bold_H ( bold_q ) italic_e start_POSTSUPERSCRIPT - italic_i italic_ω italic_t end_POSTSUPERSCRIPT ) italic_e start_POSTSUPERSCRIPT italic_i bold_q ⋅ bold_italic_ρ end_POSTSUPERSCRIPT.
- See Supplemental Material […] for the details of the density-matrix approach and time-dependent perturbation theory for the optical spin pumping.
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