KIAS workshop "From correlated electrons to nanoscale materials"

at Korea Institute for Advanced Study (KIAS), Seoul, Korea

• Heung-Sun Sim
  
  Korea Advanced Institute of Science and Technology (KAIST)
  
  

  Title

  Electron dephasing in an electronic interferometer

  Abstract

  I will discuss two nontrivial effects of electron-electron interactions on electron coherence. It has been commonly hypothesized that as a particle travels more distance, its coherence decays due to scattering with other particles, and that the decay is characterized by a single coherence length. I will first show [1] that the coherence of an electron does not follow the hypothesis in a one-dimensional quantum wire with finite length. The decay is characterized by multiple coherence lengths, applied from region to region, even though the wire is homogeneous, and the coherence can even revive after the decay. This counterintuitive behavior is due to the interaction-induced fractionalization of electrons [2,3,4] and the finite-size-induced recombination of the fractions. Second, I will consider an electronic Mach-Zehnder interferometer, recently realized using integer quantum Hall edge states. Recent experiments on it have shown a puzzling lobe structure of interference visibility and phase jumps by p as a function of bias voltage [5]. I will propose a possible origin of the puzzle [6]. The shot noise at the beam splitter of the interferometer generates an ensemble of nonequilibrium electron density configurations and electron interactions induce configuration-specific phase shifts of an interfering electron. The nonequilibrium ensemble average of the resulting interference signals gives rise to the lobe structure and the phase jumps by p. 1. J. U. Kim, W.-R. Lee, H.-W. Lee, and H.-S. Sim, preprint (2008). 2. K.-V. Pham, M. Gabay, P. Lederer, Phys. Rev. B 61, 16397 (2000). 3. H. Steinberg et al., Nature Phys. 4, 116 (2008). 4. K. Le Hur, Phys. Rev. Lett. 95, 076801 (2005). 5. I. Neder et al., Phys. Rev. Lett. 96, 016804 (2006). 6. S.-C. Youn, H.-W. Lee, and H.-S. Sim, Phys. Rev. Lett. 100, 196807 (2008).