Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526739
Title: Non-equilibrium statistics for electronic systems in low dimension
Author: Zhang, Jin
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2010
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Abstract:
The charge fluctuations in electronic devices are becoming increasingly important as the device size decreases. In this thesis, I first focus on the theory of the Full Counting Statistics (FCS) of the charge transferred across a quantum point contact, which can have a general time-dependent transparency with arbitrary pulses applied between the leads. I present two methods, one analytical and one numerical, for computing the FCS for non-interacting electrons at zero temperature. For the case of a barrier with time-dependent profile but no bias, a mapping onto the case of a biased barrier with constant transmission and reflection amplitudes is derived. For the general case, which corresponds to applying both a bias and varying the barrier profile with time, a numerical scheme for computing exactly the FCS for a device has been developed. With these tools, I discuss two applications of the FCS, both of which offer the possibility of suppressing the quantum equilibrium noise from logarithmically divergent down to constant level: an optimal electronic entangler and an on-demand low noise single electron source, which could have potential application in electronic quantum computation/information. How the deviation from an ideal pulse affects the quality of operation of a device with low noise single electron source or an entangler is discussed in depth. The response of a many-body system driven away from equilibrium is of fundamental interest. The second topic I present in this thesis is the study of probably the simplest non-trivial many-body system out of equilibrium—the non-equilibrium Fermi-edge singularity (NFES) in tunneling junctions. I first show a method which maps the NFES problem onto the problem of calculating the FCS for a fictitious system, where various methods are available. Then I focus on an interpretation on an experimental data obtained by Cobden which shows the first clear experimental observation of the NFES in tunneling devices. A generalisation of the NFES in the constant bias voltage case to non-zero temperature and low-frequency ac signal is presented. Two factors, namely the Fumi shift and the exponent, both of which are complex when the system is driven away from equilibrium, are identified to account for the measured data. Good agreement between the theory and the measured data is achieved.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council (EPSRC) (EP/D065135/1) ; University of Warwick
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.526739  DOI: Not available
Keywords: QC Physics
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