Effects of quantum noise on dephasing in mesoscopic systems

在弱局域化(WL)和普适电导涨落(UCFs)的背景下，我们研究了量子噪声对介观无序系统中电子相互作用引起的退相的影响。在这样的系统中，相互作用可以通过影响电子波函数的量子力学相位的起伏的有效噪声场来描述。然而，传导电子与该噪声场之间能量传递的相空间受到泡利阻塞的限制，因此依赖于温度T。这一最基本的影响可以用具有非零噪声关联时间TT1/T的有效量子噪声场来解释(而通常使用的经典噪声场的Tt=0)。我们将研究两种类型的系统，其中使用TT≠0是必不可少的：(I)复杂的几何结构，如由准一维导线构成的环和网格，其特征是无Thouless能量Eth(穿越环或网格牌匾的逆时间)；以及(Ii)外部交流场中的去相，其特征是AC频率ωac。对于这些情况，一旦T降到Eth或φAc以下，退相时间Tω(T)的温度依赖关系就会发生质的变化，并对涉及WL和UCFs的现象产生实验上可测量的结果。

We propose to study the effects of quantum noise on dephasing due to electronelectron interactions in mesoscopic disordered systems, in the context of weak localization (WL) and universal conductance fluctuations (UCFs). In such systems, interactions can be described via a fluctuating effective noise field affecting the quantum mechanical phase of electron wave functions. The phase space for energy transfer between conduction electrons and this noise field, however, is restricted by Pauli blocking and hence depends on the temperature T. This very fundamental effect can be accounted for by using an effective quantum noise field with a nonzero noise correlation time, TT 1/T (whereas the commonly-used classical noise field has TT = 0). We will study two types of systems for which using TT ≠ 0 is essential: (i) Complex geometries such as rings and grids constructed from quasi-1D wires, characterized by a Thouless energy ETh (the inverse time for traversing a ring or a grid plaquette); and (ii) dephasing in external AC fields, characterized by an AC frequency ωac. For these, the temperature-dependence of the dephasing time Tφ(T) changes qualitatively once T drops below ETh or ωac, with experimentally measurable consequences for phenomena involving WL and UCFs.