Bieri, Erasmus. Correlation and interference experiments with edge states. 2009, PhD Thesis, University of Basel, Faculty of Science.
Official URL: http://edoc.unibas.ch/diss/DissB_8735
as the quantization of the charge. They are characterized by the variance ∆I 2 = I 2 − I 2 , which is called noise. In addition, in multi-terminal devices, the sign of the cross correlation of ﬂuctuations between diﬀerent terminals, ∆I1 ∆I2 , can provide additional information as for instance the particle statistics. The basics of electron transport in mesoscopic systems are described in chapter 2. In phase coherent systems, interference pattern develop. Single particle or amplitude interference arises from a superposition of single-particle processes and can be seen in the mean current I which is a function of the phase diﬀerence between the individual processes. It is also possible to probe the interference capability by two-particle or intensity interference. This is a consequence of a superposition of indistinguishable two-particle processes and appears in the cross correlation ∆I1 ∆I2 of the currents between two detectors and is as well a function of the phase diﬀerence between the two-particle processes. Textbook experiments concerning interference are mostly provided by the ﬁeld of optics. An example for amplitude interference is a double slit experiment where the light passing the two slits is superposed and gives rise to an interference pattern on the screen behind. The ﬁrst intensity interference experiments have been carried out by Hanbury Brown and Twiss in 1956 [1, 2] where they examined thermal light sources. In addition to an interference pattern they measured positive correlations, which is often labeled as photon bunching and was the starting point of the ﬁeld of quantum optics [3–5]. It is interesting to compare such experiments with similar ones carried out with electrons. Because electrons interact much more with their surrounding environment, they loose their phase coherence much faster and therefore the length scales of such experiments are much smaller. However, the technical progress allows the production of such small structures, leading to realizations of electronic equivalents [6–9] with negative sign of the cross correlation (electron antibunching). A detailed discussion is given in chapter 4. In chapter 5 the experiments of Henny et al.  and Oberholzer et al. ,which used edge states as electron beams, are extended. Inspired by a proposal of Texier and Büttiker , which itself follows from a discussion of Refs. [6, 8], the impact of equilibration of current and current ﬂuctuations between such edge states due to inelastic scattering is investigated. A beam 3 splitter experiment is presented where for the ﬁrst time positive correlations have been measured in a normal-conducting Fermionic environment . In the mentioned electron anti-bunching experiments [6–9] negative cross correlation have been shown but no interference pattern because the phase diﬀerence could not be changed in these experiments. In 2004, Samuelsson et al.  proposed a realization of a two-electron interferometer using again edge states as electron beams. This proposal was inspired by the electronic Mach-Zehnder interferometer reported by Ji et al. a year before . While for an electronic Mach-Zehnder interferometer interference eﬀects are seen in the conductance, for the two-electron interferometer they only show up in intensity correlations. Compared to conductance measurements, correlation measurements are much more complex. The signal is much smaller which leads to time consuming averaging processes. In order to produce such a two-source electron interferometer the same technical challenges have to be overcome as for a single-particle Mach-Zehnder interferometer. These are e. g. the small working Ohmic contacts in the middle of the sample or the free-standing bridges. Hence, in chapter 6 of this thesis a Mach-Zehnder interferometer has been produced and characterized in a ﬁrst step in order to realize a two-source electron interferometer in a second step. Compared to other implementations of electronic Mach-Zehnder interferometers [13– 16] the visibility has been investigated for a broad range of transmission values revealing an unexpected DC bias dependence. Electronic Mach-Zehnder interferometer are very sensitive to a change of the phase diﬀerence between the two interferometer arms. Hence, as soon as they are understood good enough, they could be nice phase sensor devices to probe decoherence eﬀects.
|Committee Members:||Faist, J. and Strunk, Ch.|
|Faculties and Departments:||05 Faculty of Science > Departement Physik > Physik > Experimentalphysik Nanoeklektronik (Schönenberger)|
|Bibsysno:||Link to catalogue|
|Number of Pages:||122|
|Last Modified:||30 Jun 2016 10:41|
|Deposited On:||21 Jul 2009 14:28|
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