Electron-spin polarization in both magnetically and electrically modulated nanostructures

We investigate theoretically the spin-dependent transport properties of electrons in realistic magnetic-electric-barrier (MEB) nanostructures produced by the deposition, onto a heterostructure, of a metallic ferromagnetic stripe. We find the degree of electron-spin polarization to be closely tied to the voltage applied to the stripe, despite the fact that this voltage in itself induces no spin-polarization effect. As a positive (negative) voltage is applied, the electron-spin polarization shifts in the low- (high-) energy direction and increases (decreases). Our results imply that the degree of electron-spin polarization can be tuned through the applied voltage. This implication might prove useful in the design and application of spintronic devices based on magnetic-barrier nanostructures. PACS Nos.: 73.40.Gk, 73.23.-b, 75.70.Cn

Article

The quantum dynamics of a Xe atom placed on the STM surfaceis studied considering two important types of nonstationary externalforces. These are the driving forces appearing during the application of avoltage pulse, and the fluctuating forces determined by the coupling to anOhmic environment. The localization probability on the tipduring voltage pulses of 20 and 7 ns with symmetric triangular andtrapezoidal shapes is calculated neglecting the environmental interactions.The results indicate that the atom dynamics in this case is reversible, andafter the pulse the transfer probability is small.The effects of the fluctuating forces produced by the coupling to thesurrounding electrons and surface phonons are studied in a static potential.It is shown that the thermal fluctuations at the environmental temperaturecan lead to irreversible atom tunneling through the potential barrier,described by an exponential decay law.PACS Nos.: 61.16.Di, 73.40.Gk, 05.40.+j

A New Computational Approach to Photon-Assisted Tunneling in Intense Driving Fields Based on a Fabry-Perot Analogy

Quantum transport in multiple-barrier systems exposed to intense laser fields is investigated by employing an analogy with the Fabry-Perot interferometer of classical optics. This analogy is exact if no further approximations are introduced. The Fabry- Perot approach is shown to be quite robust: Approximating the barriers by δ-functions with equivalent dc transmission and reflection amplitudes still yields excellent agreement with “exact” orthodox transfer-matrix calculations. The advantage of the former is its much reduced computational demands as well as ease of use. 73.40.Gk, 73.50.Pz, 72.40. + w, 42.50.Hz.