In this talk, I will first give an introduction to dephasing, i.e. the loss of quantum-mechanical phase coherence by a fluctuating environment. I will then turn to the electronic Mach-Zehnder interferometer which has become a prime tool to investigate dephasing of ballistic electrons in the solid state environment.
Two aspects will be discussed in more detail: When dephasing is due to the shot noise of an adjacent edge channel, the discreteness of charges implies that the potential fluctuations are non-Gaussian. We have shown that this leads to oscillations in the interference contrast of the interferometer, in contrast to naive expectations. At high bias voltages, we deal with dephasing in a strongly nonequilibrium situation. We have analyzed dephasing by electron- electron interactions in that situation using a straightforward and physically transparent ‘semiclassical’ approach.
The Green’s function (i.e. the interference contrast) of a chiral interacting one-dimensional fermion system (edge channel) obeys a power-law decay at high energies, at zero temperature. Surprisingly, we find that the exponent is universal, i.e. independent of the interaction strength, for (almost) arbitrarily shaped interaction potentials.
[1] “Controlled Dephasing of Electrons by Non-Gaussian Shot Noise”, I. Neder, F. Marquardt, M. Heiblum, D. Mahalu, and V. Umansky, Nature Physics textbf{3}, 534 (2007)
[2] “Coherence oscillations in dephasing by non-Gaussian shot noise”, I. Neder and F. Marquardt, New Journal of Physics textbf{9}, 112 (2007)
[3] “Universal Dephasing in a Chiral 1D Interacting Fermion System”, Clemens Neuenhahn and Florian Marquardt, Physical Review Letters textbf{102}, 046806 (2009)
Ludwig-Maximilians University Munich