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arXiv 0707.3245cond-mat.mes-hallcond-mat.stat-mech
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开放介观金属环中的电子输运

Electron transport in an open mesoscopic metallic ring

Dibyendu Roy

摘要:

我们研究了电子输运在一个正常的金属环模拟的紧束缚晶格哈密顿量,耦合到两个电子水库。首先,Buttiker的模型,将非弹性散射,因此消相干和耗散,已被扩展的每个网站的开放环连接到一维导线均匀移相的环螺纹的磁通量。我们表明,与此扩展电导保持对称下的磁通反转,和Aharonov-Bohm振荡与变化的磁通量减少到零的退相干参数的函数,从而表明在环中的退相。这种扩展使我们能够找到当地的化学势轮廓的环网站与变化的磁通量和退相干参数类似的四探针测量。由于量子干涉效应,局部电化学电势在环位置振荡。它预测测量的四点电阻也会波动,甚至可能是负数。然后,我们指出了封闭环的电子本征态的作用,在持续电流周围的Fano反共振的一个不对称的开放环的理想引线和隧道势垒。通过确定环的非厄米有效哈密顿量的实本征值,我们证明了即使在没有磁通量的情况下,非对称环的散射态连续体中仍存在离散束缚态.我们的方法涉及量子朗之万方程和非平衡格林函数。

英文摘要:

We study electron transport in a normal-metal ring modeled by the tight binding lattice Hamiltonian, coupled to two electron reservoirs. First, Buttiker's model of incorporating inelastic scattering, hence decoherence and dissipation, has been extended by connecting each site of the open ring to one-dimensional leads for uniform dephasing in the ring threaded by magnetic flux. We show with this extension conductance remains symmetric under flux reversal, and Aharonov-Bohm oscillations with changing magnetic flux reduce to zero as a function of the decoherence parameter, thus indicating dephasing in the ring. This extension enables us to find local chemical potential profiles of the ring sites with changing magnetic flux and the decoherence parameter analogously to the four probe measurement. The local electrochemical potential oscillates in the ring sites because of quantum-interference effects. It predicts that measured four-point resistance also fluctuates and even can be negative. Then we point out the role of the closed ring's electronic eigenstates in the persistent current around Fano antiresonances of an asymmetric open ring for both ideal leads and tunnel barriers. Determining the real eigenvalues of the non-Hermitian effective Hamiltonian of the ring, we show that there exist discrete bound states in the continuum of scattering states for the asymmetric ring even in the absence of magnetic flux. Our approach involves quantum Langevin equations and non-equilibrium Green's functions.

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