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arXiv 1002.3580cond-mat.mes-hall
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介观干涉仪中的磁非对称输运:从弱耦合到强耦合

Magnetoasymmetric transport in a mesoscopic interferometer: From the weak to the strong coupling regime

Jong Soo Lim, David Sanchez, Rosa Lopez

摘要:

微可逆性原理意味着两端Aharonov-Bohm干涉仪的电导是外加磁通量的偶函数。然而,远离线性响应,该对称性不被满足,并且当量子点被插入其臂中的一个中时,干涉仪的电导相位可以是偏置电压的连续函数。这种磁不对称性已经在相关的介观系统中进行了研究,并且是由于导体的内部电势在平衡状态下的不对称响应而引起的。在这里,我们讨论的量子点Aharonov-Bohm干涉仪的磁不对称性时,强电子-电子相互作用被考虑到超出平均场的方法。我们发现,在很低的温度下,微分电导的不对称元素显示出一个突变的费米能级附近的电压。在较高的温度下,我们恢复作为偏置的函数的磁不对称性的平滑变化。我们说明了我们的结果与援助的电子占领在点,表明其非平衡分量是一个不对称的功能的磁通量,甚至最低阶的电压。我们还计算了电流-电流相关性(噪声)的磁不对称性,发现它在很大程度上是由弱非线性电导项的磁不对称性给出的。因此,这两个磁不对称性(噪声和电导)通过高阶波动耗散关系相互关联。这一结果似乎是真实的,即使在低温制度,近藤物理和多体效应占主导地位的传输特性。

英文摘要:

The microreversibility principle implies that the conductance of a two-terminal Aharonov-Bohm interferometer is an even function of the applied magnetic flux. Away from linear response, however, this symmetry is not fulfilled and the conductance phase of the interferometer when a quantum dot is inserted in one of its arms can be a continuous function of the bias voltage. Such magnetoasymmetries have been investigated in related mesoscopic systems and arise as a consequence of the asymetric response of the internal potential of the conductor out of equilibrium. Here we discuss magnetoasymmetries in quantum-dot Aharonov-Bohm interferometers when strong electron-electron interactions are taken into account beyond the mean-field approach. We find that at very low temperatures the asymmetric element of the differential conductance shows an abrupt change for voltages around the Fermi level. At higher temperatures we recover a smooth variation of the magnetoasymmetry as a function of the bias. We illustrate our results with the aid of the electron occupation at the dot, demonstrating that its nonequilibrium component is an asymmetric function of the flux even to lowest order in voltage. We also calculate the magnetoasymmetry of the current-current correlations (the noise) and find that it is given, to a good extent, by the magnetoasymmetry of the weakly nonlinear conductance term. Therefore, both magnetoasymmetries (noise and conductance) are related to each other via a higher-order fluctuation-dissipation relation. This result appears to be true even in the low temperature regime, where Kondo physics and many-body effects dominate the transport properties.

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