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一年以前 ,人们惊奇地发现 :在相当弱的磁场中 ,并不太强的微波辐照就可以使二维半导体的磁阻产生强烈的振荡 ,振幅的最大值可超过无辐照磁阻值的十几倍 ,最小值可以一直降到零 .全世界众多的凝聚态物理学家争相聚焦到这个领域 ,进行了许多实验和理论研究 ,企图弄清这一意外发现的机理 .经过一年多的努力 ,人们已经掌握了这个现象更多的细节 ,对其物理机制也有了初步了解 .但深入的实验和理论探索可能还要继续相当一段时间 .文章将对这个物理现象及相关的理论模型 ,尤其是目前得到较多赞同的光子辅助磁输运模型 ,作一简单的介绍 . 相似文献
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Within the framework of the Floquet theorem, we have
investigated single-electron photon-assisted tunneling in a
double-well system using the transfer matrix technique. The
transmission probability displays satellite peaks on the both sides
of main resonance peaks and these satellite peaks originate from
emission or absorption photons. The single-electron resonance
tunneling can be control through changing applied harmonically
potential positions, such as driven potential in wells, in barriers,
or in whole double-well system. This advantage should be useful in
the optimization of the parameters of a transmission device. 相似文献
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Photon-assisted and spin-dependent shot noise in magnetic-field tunable ZnSe/Zn_(1-x)Mn_xSe structures 下载免费PDF全文
We have investigated the photon-assisted shot noise properties in the magnetic field tunable heterostructures. Transport properties of the model structure are strongly dependent on the oscillatory field and the magnetic field. In this structure,electrons can absorb or emit one or multi-photons to reach the quasi-bound state. As a result, the transmission properties are affected considerably by photon-assisted tunneling and these features cause the nontrivial variations in the shot noise and Fano factor. It is found that the shot noise becomes spin-dependent and can be modulated not only by the magnetic field, but also by the oscillatory field. Both the spin-up and spin-down components of the shot noise can be greatly suppressed by the magnetic field, and can also be drastically enhanced by the harmonically driven field. Furthermore,with increasing external magnetic field, it is important to note that the enhanced intensity is decreased, even suppressed.These results suggest another method to suppress the shot noise via modulating the oscillatory field at a diluted-magneticsemiconductors/semiconductor structure. 相似文献
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在超声射流条件下.采用SF6/Ar(~10%)混合气束脉冲直流放电方法产生S2自由基,观测了32S2自由基在30000~35500 cm-1波段的激光诱导荧光激发谱.通过对所观测到的40多个振动谱带的归属,确定其中28个谱带为s2自由基B3∑μ一X3∑-g跃迁的(v'=1-9,0),(v'=1-8,1),(v'=1-7,2)和(v'=2-5,3)四个谱带序列.通过对所获谱带的转动分析,得到更为丰富的S2自由基B3∑-μ-X3∑-g跃迁谱带的转动光谱常数和更为精确的B3∑-μ电子态的平衡分子常数:Te,щe,щXe,Be,ae和Re.另外,还测得所有观测到的谱带的寿命,进一步丰富了S2自由基学∑-μ-X2∑-g跃迁谱带的光谱信息. 相似文献
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SONG Hong-Yan WU Liu-Po SHI Yao-Ming ZHOU Shi-Ping 《理论物理通讯》2008,49(3):767-770
We investigate transport through a perfect quantum wire with a
side-coupled quantum dot under an ac field. Time-averaged complex
conductance is formulated by using the nonequilibrium Green function
(NGF) method. We find that the electron-photon interaction together
with the quantum interference of electron wave function can lead to
anti-resonance in the conductance, which is then useful for tuning
coherence and phases of electrons. Meanwhile, we study the
temperature dependence of the conductance. Interestingly, a
peak-structure can be developed at the Fano resonance levels with
increasing temperatures. 相似文献
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An analytical formula of the tunneling current through a coupled double-quantumdot system in the presence of a time-dependent electric field is obtained by using the Keldysh nonequilibrium Green's function technique. The dependence of the time-averaged current on the frequency of the electric field, as well as the dependence of the multiphoton assisted tunneling on the strength of the electric field are studied. The features of I-Vdc characteristic are also investigated. Besides, we present a simplified formula which can be used to determine the heights of the resonant peaks conveniently. 相似文献
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Photon-assisted electronic and spin transport through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm interferometer 下载免费PDF全文
We investigate the time-modulated electronic and spin transport properties through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm(A-B) interferometer. By using the Keldysh non-equilibrium Green's function technique, the photon-assisted spin-dependent average current is analyzed. The T-shaped three-quantum-dot molecule A-B interferometer exhibits excellent controllability in the average current resonance spectra by adjusting the interdot coupling strength, Rashba spin-orbit coupling strength, magnetic flux, and amplitude of the time-dependent external field.Efficient spin filtering and multiple electron-photon pump functions are exploited in the multi-quantum-dot molecule A-B interferometer by a time-modulated external field. 相似文献
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应用非平衡格林函数方法,研究了带有微波调制的侧向耦合量子点的量子线中的光辅助隧穿.在考虑了量子干涉和微波场的情况下,得出并讨论了电子传榆幅度和相位方面的信息.电子传输幅度显示出一系列的反共振峰(对应图中的谷结构).峰值的高度与振荡的微波场的幅度和频率有关,而峰的位置只与微波场的频率有关.在有限温的情况下,反共振峰值的高度随着温度的增加而减小,当温度足够高时,反共振峰会消失,特别地,在一定的温度下,低温下谷的地方会演变成峰. 相似文献
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