Effects of quantum noise on dephasing in mesoscopic systems

• Applicant: Professor Dr. Jan von Delft
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 185960027

• Final Report Year: 2014

Final Report Abstract

The transition from quantum to classical behavior of complex systems, known as dephasing, has fascinated physicists during the last decades. Disordered systems provide an instructive environment to study the dephasing rate γ, since electron interference leads to quantum corrections to classical quantities, such as the weak-localization correction ∆g to the conductance, whose magnitude is governed by γ. In this project, we have studied 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 ω of electron interactions to ω T , which leads to a decrease of γ. However, the so-called 0D regime of dephasing, reached at T << ETh , is practically the only relevant regime, in which Pauli blocking significantly influences the temperature dependence of γ. Despite of its fundamental physical importance, 0D dephasing has not been observed experimentally in the past. We have investigated several possible scenarios for verifying its existence: (1) We analyzed the temperature dependence of ∆g in open and confined systems and gave detailed instructions on how the crossover to 0D dephasing can be reliably detected. Two concrete examples were studied: an almost isolated ring and a new quantum dot model. However, we concluded that in transport experiments, 0D dephasing unavoidably occurs in the universal regime, in which all quantum corrections to the conductance depend only weakly on γ, and hence carry only weak signatures of 0D dephasing. (2) We studied the quantum corrections to the polarizability ∆α of isolated systems, and derived their dependence on γ and temperature. We showed that 0D dephasing occurs in a temperature range in which ∆α depends strongly (as a power-law) on γ, making the quantum corrections to the polarizability an ideal candidate to study dephasing at low temperatures and the influence of Pauli blocking.

Publications

• Thermal noise and dephasing due to electron interactions in nontrivial geometries, Physical Review B 84, 054204 (2011)
  M. Treiber, C. Texier, O. M. Yevtushenko, J. von Delft, and I. V. Lerner
  
• Transport and dephasing in a quantum dot: Multiply connected graph model, Annalen der Physik (Berlin) 524, 188 (2012)
  M. Treiber, O. M. Yevtushenko, F. Marquardt, J. von Delft, and I. V. Lerner
  
• Quantum Corrections to the Polarizability and Dephasing in Isolated Disordered Metals, Physical Review B 88, 024201 (2013)
  M. Treiber, P. M. Ostrovsky, O. M. Yevtushenko, J. von Delft, and I. V. Lerner