title: Self-polarized spin-nanolasers.
abstract: Besides adding a new functionality to conventional lasers, spin-polarized lasers can, potentially, offer lower threshold currents and reach higher emission intensities. However, to achieve spin-polarized lasing emission a material should possess a slow spin relaxation and a high propensity to be injected with spin-polarized currents. These are stringent requirements that, so far, have limited the choice of candidate materials for spin-lasers. Here we show that these requirements can be relaxed by using a new self-polarized spin mechanism. Fe3O4 nanoparticles are coupled to GaN nanorods to form an energy-band structure that induces the selective charge transfer of electrons with opposite spins. In turn, this selection mechanism generates the population imbalance between spin-up and spin-down electrons in the emitter's energy levels without an external bias. Using this principle, we demonstrate laser emission from GaN nanorods with spin polarization up to 28.2% at room temperature under a low magnetic field of 0.35 T. As the spin-selection mechanism relies entirely on the relative energy-band alignment between the iron oxide nanoparticles and the emitter and requires neither optical pumping with circularly polarized light nor electrical pumping with magnetic electrodes, potentially a wide range of semiconductors can be used as spin-nanolasers.
authors.affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Ju-Ying
authors.initials: JY
authors.lastname: Chen
authors.affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Tong-Ming
authors.initials: TM
authors.lastname: Wong
authors.affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Che-Wei
authors.initials: CW
authors.lastname: Chang
authors.affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Chen-Yuan
authors.initials: CY
authors.lastname: Dong
authors.affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Yang-Fang
authors.initials: YF
authors.lastname: Chen