31,250 research outputs found
Local spin polarisation of electrons in Rashba semiconductor nanowires: effects of the bound state
The local spin polarisation (LSP) of electrons in two typical semiconductor
nanowires under the modulation of Rashba spin-orbit interaction (SOI) is
investigated theoretically. The influence of both the SOI- and
structure-induced bound states on the LSP is taken into account via the
spin-resolved lattice Green function method. It is discovered that high
spin-density islands with alternative signs of polarisation are formed inside
the nanowires due to the interaction between the bound states and the Rashba
effective magnetic field. Further study shows that the spin-density islands
caused by the structure-induced bound state exhibit a strong robustness against
disorder. These findings may provide an efficient way to create local magnetic
moments and store information in semiconductors.Comment: 8 pages, 3 figure
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A low-bandgap dimeric porphyrin molecule for 10% efficiency solar cells with small photon energy loss
Dimeric porphyrin molecules have great potential as donor materials for high performance bulk heterojunction organic solar cells (OSCs). Recently reported dimeric porphyrins bridged by ethynylenes showed power conversion efficiencies (PCEs) of more than 8%. In this study, we design and synthesize a new conjugated dimeric D-A porphyrin ZnP2BT-RH, in which the two porphyrin units are linked by an electron accepting benzothiadiazole (BT) unit. The introduction of the BT unit enhances the electron delocalization, resulting in a lower highest occupied molecular orbital (HOMO) energy level and an increased molar extinction coefficient in the near-infrared (NIR) region. The bulk heterojunction solar cells with ZnP2BT-RH as the donor material exhibit a high PCE of up to 10% with a low energy loss (Eloss) of only 0.56 eV. The 10% PCE is the highest for porphyrin-based OSCs with a conventional structure, and this Eloss is also the smallest among those reported for small molecule-based OSCs with a PCE higher than 10% to date
Detecting Extra Dimension by Helium-like Ions
Considering that gravitational force might deviate from Newton's
inverse-square law and become much stronger in small scale, we present a method
to detect the possible existence of extra dimensions in the ADD model. By
making use of an effective variational wave function, we obtain the
nonrelativistic ground energy of a helium atom and its isoelectronic sequence.
Based on these results, we calculate gravity correction of the ADD model. Our
calculation may provide a rough estimation about the magnitude of the
corresponding frequencies which could be measured in later experiments.Comment: 8 pages, no figures, accepted by Mod. Phys. Lett.
Dynamics of Vortex Core Switching in Ferromagnetic Nanodisks
Dynamics of magnetic vortex core switching in nanometer-scale permalloy disk,
having a single vortex ground state, was investigated by micromagnetic
modeling. When an in-plane magnetic field pulse with an appropriate strength
and duration is applied to the vortex structure, additional two vortices, i.e.,
a circular- and an anti-vortex, are created near the original vortex core.
Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at
the annihilation point and propagated through the entire element; the relaxed
state for the system is the single vortex state with a switched vortex core.Comment: to appear in Appl. Phys. Let
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