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1.
李玉现 《中国物理 B》2008,17(8):3058-3061
Using the tight-binding model approximation, this paper investigates theoretically spin-dependent quantum transport through an Aharonov-Bohm (AB) interferometer. An external magnetic field is applied to produce the spinpolarization and spin current. The AB interferometer, acting as a spin splitter, separates the opposite spin polarization current. By adjusting the energy and the direction of the magnetic field, large spin-polarized current can be obtained.  相似文献   
2.
安兴涛  李玉现  刘建军 《物理学报》2007,56(7):4105-4112
描述了介观物理系统中噪声的研究现况. 对热噪声和散粒噪声的物理起源做了详细介绍,热噪声是系统的能态占据数发生涨落引起的,而散粒噪声源于载流子传输的微粒特性. 还介绍了研究噪声的主要理论——散射理论,并给出了其在马鞍形半导体量子线和铁磁/绝缘体/半导体双异质结两种介观系统中的应用,指出了噪声研究的实际物理意义. 关键词: 介观物理 热噪声 散粒噪声 散射理论  相似文献   
3.
李玉现 《中国物理快报》2008,25(10):3739-3741
Spin-dependent Andreev reflection and spin polarization through a diluted magnetic semiconductor quantum wire coupled to normal metallic and superconductor electrodes are investigated using scattering theory. When the spin-orbit coupling is considered, more Andreev conductance steps appear at the same Fermi energy. Magnetic semiconductor quantum wire separates the spin-up and spin-down electrons. The Fermi energy, at which different- spin-state electrons begin to separate, becomes lower due to the effect of the spin-orbit interaction. The spin filter effect can be measured more easily by investigating the Andreev conductance than by investigating the normal conductance.  相似文献   
4.
李玉现  刘建军  李伯臧 《物理学报》2005,54(3):1366-1369
在有限温度和不同磁场下,精确计算了各种鞍形量子点接触中的量子化电导和热功率.量子点接触的形状影响体系的量子化特征.随磁场的增加,量子化电导的台阶加宽,热功率共振峰之间的距离加长,共振峰的数量减少.当温度升高时,电导的量子化被破坏,热功率的峰状结构也逐渐消失. 关键词: 量子点接触 量子化电导 热功率 磁场  相似文献   
5.
王素新  李玉现  刘建军 《中国物理 B》2016,25(3):37304-037304
Andreev reflection(AR) in a normal-metal/quantum-dot/superconductor(N–QD–S) system with coupled Majorana bound states(MBSs) is investigated theoretically. We find that in the N–QD–S system, the AR can be enhanced when coupling to the MBSs is incorporated. Fano line-shapes can be observed in the AR conductance spectrum when there is an appropriate QD–MBS coupling or MBS–MBS coupling. The AR conductance is always e~2/2h at the zero Fermi energy point when only QD–MBSs coupling is considered. In addition, the resonant AR occurs when the MBS–MBS coupling roughly equals to the QD energy level. We also find that an AR antiresonance appears when the QD energy level approximately equals to the sum of the QD–MBS coupling and the MBS–MBS coupling. These features may serve as characteristic signatures for the probe of MBSs.  相似文献   
6.
A spin device with three normal metal leads via triple quantum dot in the presence of Rashba spin-orbit interaction is proposed, which is free from magnetic field or magnetic material. Using nonequilibrium Green's function technique, we investigate the spin current through the three-quantum-dot device. It is found that the spin current can be affected by the strength of the Rashba spin-orbit interaction, Coulomb interaction, the energy of the quantum dot and the bias voltage of the lead. The periodic oscillation of spin current can be controlled by tuning the Rashba spin-orbit interaction.  相似文献   
7.
杜坚  张鹏  刘继红  李金亮  李玉现 《物理学报》2008,57(11):7221-7227
研究了含δ势垒的铁磁/半导体/铁磁异质结中自旋相关的透射概率和渡越时间,讨论了量子尺寸效应和Rashba自旋轨道耦合效应对隧穿特性的影响.研究结果表明:δ势垒的存在降低了自旋电子的透射概率,改变了透射概率的位相.Rashba自旋轨道耦合强度的增加加大了透射概率的振荡频率.不同自旋取向的电子隧穿异质结时,渡越时间随着半导体长度、Rashba自旋轨道耦合强度以及两铁磁电极中的磁化方向的夹角的变化而变化. 关键词: δ势垒')" href="#">δ势垒 铁磁/半导体/铁磁异质结 Rashba自旋轨道耦合效应 渡越时间  相似文献   
8.
谢征微  李伯臧  李玉现 《中国物理》2002,11(10):1060-1065
Based on the free-electron approximation,we investigate the effect of the ferromagnetic metal layer on the tunnelling magnetoresistance(TMR) and tunnelling conductance(TC)in the double magnetic tunnel junctions(DMTJs) of the structure NM/FM/I(S)/NM/I(S)/FM/NM,where FM,NM and I(S) represent the ferromagnetic metal,nonmagetic metal and insulator(Semiconductor),respectively,The FM,I(S)and inner NM layers are of finite thickness,while the thickness of the outer NM layer is infinite.The calculated results show that,due to the spin-dependent interfacial potential barriers caused by electronic band mismatch between the various magnetic and nonmagnetic layers,the dependences of the TMR and TC on the thicknesses of the FM layers exhibit oscillations,and a much higher TMR can be obtained for suitable thicknesses of FM layers.  相似文献   
9.
李玉现  李伯臧 《中国物理》2005,14(5):1021-1024
利用传递矩阵方法,我们计算了自旋轨道耦合和磁场对准一维铁磁/半导体/铁磁系统中电子输运性质的影响。计算结果发现,透射系数的振幅随磁场增加而增大。在反铁磁排列时,即使在磁场作用下,上、下自旋电子具有相同的透射系数。与不加磁场时的情况相反,在一定的磁场和耦合强度时,铁磁排列中,上自旋电子的透射系数大于下自旋电子的,而且出现了自旋反转。  相似文献   
10.
王素新  李玉现  王宁  刘建军 《物理学报》2016,65(13):137302-137302
研究了连接在正常金属电极和超导电极之间的耦合Majorana束缚态(MBSs)T形双量子点结构中的Andreev反射.研究发现,对于T形双量子点结构,当入射能量等于边耦合量子点能级时Andreev反射电导出现Fano振荡,连接MBSs之后,零费米能附近出现一对新的Fano型振荡峰.如果忽略两个MBSs之间的相互作用,零费米能点的Andreev反射电导为定值1/2G_0(G_0=2e~2/h),不受量子点能级、双量子点之间耦合强度以及量子点与MBSs之间的耦合强度的影响.此外,在没有耦合MBSs的T形双量子点结构中,调节双量子点间的耦合强度可以使零费米能附近的Andreev反射电导出现由共振带向反共振带的转变,而耦合MBSs之后,又可以使反共振消失转而出现新的共振峰.  相似文献   
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