Exciton condensation and perfect Coulomb drag
Exciton condensation and perfect Coulomb drag
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DOI：
10.1038/nature11302
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发表时间：
2012-08-23
期刊：
影响因子：
64.8
通讯作者：
West, K. W.
中科院分区：
文献类型：
--
作者：
Nandi, D.;Finck, A. D. K.;West, K. W.
库仑阻力是一个过程，空间上分离的导体中电子之间的排斥相互作用使得在一个导体中流动的电流能够在另一个导体中引起电压降(1-3)。如果第二导体是闭合电路的一部分，则净电流将在该电路中流动。由于库仑相互作用的严格屏蔽，拖曳电流通常比驱动电流小得多。然而，在极少数情况下，两个导体之间存在强电子相关性。例如，双量子阱系统可以支持激子凝聚，其中一个阱中的电子与另一个阱中的空穴紧密结合(4-6)。因此，预期会有“完美”的阻力；通过一个量子阱驱动的电子的稳定传输电流应该伴随着另一个量子阱中相等的空穴电流(7)。在这里，我们演示了这种效应，注意确保电子空穴对主导传输，并且量子阱之间的电荷隧道可以忽略不计，这很容易影响阻力测量。我们注意到，从电气工程的角度来看，完美的库仑阻力类似于在零频率下工作的电力变压器。
Coulomb drag is a process whereby the repulsive interactions between electrons in spatially separated conductors enable a current flowing in one of the conductors to induce a voltage drop in the other(1-3). If the second conductor is part of a closed circuit, a net current will flow in that circuit. The drag current is typically much smaller than the drive current owing to the heavy screening of the Coulomb interaction. There are, however, rare situations in which strong electronic correlations exist between the two conductors. For example, double quantum well systems can support exciton condensates, which consist of electrons in one well tightly bound to holes in the other(4-6). 'Perfect' drag is therefore expected; a steady transport current of electrons driven through one quantum well should be accompanied by an equal current of holes in the other(7). Here we demonstrate this effect, taking care to ensure that the electron-hole pairs dominate the transport and that tunnelling of charge between the quantum wells, which can readily compromise drag measurements, is negligible. We note that, from an electrical engineering perspective, perfect Coulomb drag is analogous to an electrical transformer that functions at zero frequency.