Scattering approach to time-dependent charge and energy transport in mesoscopic conductors

Abstract

This thesis aims to contribute to the field of time controlled charge and energy transport in mesoscopic systems.

In Chapter 1, Chapter 2 and Chapter 3 a short review of the scattering matrix theory is presented,

including both charge and energy transport,

useful to understand the mathematical landscape used in Papers I, II, III and IV. Chapter 3 briefly presents

the thermoelectric properties of mesoscopic conductors, investigated through the analysis of experimental data in Paper IV.

Scattering matrix theory is a powerful tool to study the current and the fluctuations of a stream of electrons.

It is in fact possible to fully characterise the distribution of charge and energy transfer in terms of the scattering matrix.

In Chapter 4 the reader is provided with the basics of the full counting statistics used in Papers I and III.

In Chapter 5 mesoscopic transport in the quantum Hall regime is presented, being the background of

the works presented in Papers I, II and III.

Chapter 6 is a brief overview of the "history"

of electron pumping and of the state of the art of this interesting field. It provides the

motivations to our new single particle source proposed in Paper I and further analysed in Paper II.

Abstract (Swedish)

Popular Abstract in English

Technological devices in our society are used on a daily basis. The speed in processing jobs and the memory capacity

are two key parameters used to set their prices.

The information is encoded with a binary system physically implemented on semiconductor circuits,

where the bit 1 corresponds to a finite voltage and the bit

0 to zero voltage. In order to increase the speed and the memory of an electronic device, its compounds need to become smaller.

The miniaturisation of electronic devices is a well known trend in engineering since the '70s.

In last decades great research efforts have been devoted to propose, study and experimentally realise nanoscale and mesoscopic solid-state systems

which, in principle, could be integrated with more conventional technology. A nanoscale object for example is a a chain of ten atoms. One nanometer is the billionth part of a meter.





Mesoscopic scale devices are constituted by large number of atoms, but, as the nanoscale ones, they are not ruled by classical physics law.

At this scale interesting effects due to quantum mechanics, i.e. the dual nature of the electrons, arise

opening a new world of possibilities for new kinds of technology.



When speaking about the dual nature of electrons flowing (current) we refer

to the fact that we can think about them as travelling particles or as propagating waves.

The choice of the picture depends on the physical problem we deal with. In mesoscopic physics most often he best

is to consider both models. When looking at the electron as a particle we can better understand the consequences of charge

quantization. The charge of an object, in fact, is given by an integer number of charge units, e, which is the charge of one electron.

When thinking about the electron as waves we can better understand the scattering properties of them. A wave against a

dam can be reflected back or overcome it or split into two parts, one reflected back and one transmitted above the barrier.

A travelling electron behaves in a similar way when scattering against an obstacle. It will b transmitted with probability T

and reflected with probability R. If the obstacle is the complicated structure of a device the incoming electron can be transmitted with different probabilities to different spots of the structure.





The development of electronic device thus depends, first, on our capability to understand, describe and predict these effects,

and second, to design

and realise prototypes to control in time and space the transport of charge and its fluctuations in a useful manner.







Electrons are however not only charge carriers but they transport energy as well. Thus,

the study of energy transport properties in mesoscopic system therefore comes as a natural consequence of the efforts to

design mesoscopic electron transport for device applications.

• author: Battista, Francesca
• supervisor: Peter Samuelsson
• opponent: Professor Martin, Thierry, Université de la Méditérannée
• organization: Mathematical Physics; NanoLund: Centre for Nanoscience
• publishing date: 2013
• type: Thesis
• publication status: published
• subject: Condensed Matter Physics
• keywords: Fysicumarkivet A:2013:Battista
• defense location: Rydberg Hall, Physics department, Lund
• defense date: 2013-01-25 10:00:00
• language: English
• LU publication?: yes
• id: 705405e6-a170-42b5-b0e5-9a4e3ca29844 (old id 3290257)
• date added to LUP: 2016-04-04 10:54:32
• date last changed: 2018-11-21 22:52:32