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Treiber, Maximilian (2013): Dephasing in disordered systems at low temperatures. Dissertation, LMU München: Fakultät für Physik



The transition from quantum to classical behavior of complex systems, known as dephasing, has fascinated physicists during the last decades. Disordered systems provide an insightful environment to study the dephasing time \tau_\varphi, since electron interference leads to quantum corrections to classical quantities, such as the weak- localization correction \Delta g to the conductance, whose magnitude is governed by \tau_\varphi. In this thesis, we study one of the fundamental questions in this field: How does Pauli blocking influence the interaction-induced dephasing time at low temperatures? In general, Pauli blocking limits the energy transfer \omega of electron interactions to \omega \ll T, which leads to an increase of \tau_\varphi. However, the so-called 0D regime of dephasing, reached at T \ll E_{Th}, is practically the only relevant regime, in which Pauli blocking significantly influences the temperature dependence of \tau_\varphi. Despite of its fundamental physical importance, 0D dephasing has not been observed experimentally in the past. We investigate several possible scenarios for verifying its existence: (1) We analyze the temperature dependence of \Delta g in open and confined systems and give detailed instructions on how the crossover to 0D dephasing can be reliably detected. Two concrete examples are studied: an almost isolated ring and a new quantum dot model. However, we conclude that in transport experiments, 0D dephasing unavoidably occurs in the universal regime, in which all quantum corrections to the conductance depend only weakly on \tau_\varphi, and hence carry only weak signatures of 0D dephasing. (2) We study the quantum corrections to the polarizability \Delta \alpha of isolated systems, and derive their dependence on \tau_\varphi and temperature. We show that \tZeroD dephasing occurs in a temperature range, in which \Delta \alpha depends strongly (as a power-law) on \tau_\varphi, making the quantum corrections to the polarizability an ideal candidate to study dephasing at low temperatures and the influence of Pauli blocking.