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arXiv 1106.2237cond-mat.dis-nncond-mat.mes-hallcond-mat.str-el
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二维量子偶极子的局域化和临界扩散

Localization and critical diffusion of quantum dipoles in two dimensions

I. L. Aleiner, B. L. Altshuler, K. B. Efetov

摘要:

我们讨论了二维偶极激发的量子传播。该问题与传统的安德森局域化不同,因为存在长距离跳变。我们发现偶极子的临界波函数总是存在的,它表现为一个与尺度无关的扩散常数。如果系统是T-不变的,则状态对于所有参数值都是临界的。否则,在这种“普通”扩散和Levy-flights之间可能存在“金属-绝缘体”过渡(扩散常数随尺度递增)。这些结果来自于改进的非线性超矩阵$σ$模型的双环分析。

英文摘要:

We discuss quantum propagation of dipole excitations in two dimensions. This problem differs from the conventional Anderson localization due to existence of long range hops. We found that the critical wavefunctions of the dipoles always exist which manifest themselves by a scale independent diffusion constant. If the system is T-invariant the states are critical for all values of the parameters. Otherwise, there can be a "metal-insulator" transition between this "ordinary" diffusion and the Levy-flights (the diffusion constant logarithmically increasing with the scale). These results follow from the two-loop analysis of the modified non-linear supermatrix $σ$-model.

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