Andreev tunneling and quasiparticle excitations in mesoscopic normal metal - superconductor structures

Dissertation

Ville F. Maisi

Research output: ThesisDissertationCollection of Articles

Abstract

Mesoscopic physics deals with systems whose size is between everyday macroscopic scale and the microscopic scale of individual atoms. With mesoscopic structures the flow of single electrons can be controlled. This thesis focuses on the control of single electrons with normal metal - superconductor structures. The emphasis is put on understanding the limitations of the control in the so-called SINIS turnstile, which is a device transporting one electron at a time. By repeating the drive with frequency f, the resulting electrical current in ideal operation I = ef could be utilized as the new definition in the SI unit system. Here e is the elementary charge. In the first part of the thesis, we review the physics of tunnel-coupled normal metals and superconductors and present the operation principle of the SINIS turnstile. We then show parallel operation of ten such devices. This allows one to reach larger currents required for high accuracy measurements. In addition we show that the experimental setup needs to be carefully designed in order to avoid spurious effects due to environmentally assisted tunneling. The second part of the thesis focuses on Andreev tunneling. In this process two electrons tunnel at once in form of a Cooper pair. Andreev tunneling leads to transfer errors, when the tunneling of a single electron is preferred. We discuss the experimental detection techniques of Andreev tunneling based on direct current measurements as well as on electron counting. Furthermore, we show experimentally that by having large enough energy cost for charging the structures, achieved by decreasing the size of the system, Andreev tunneling is suppressed and the accuracy of the turnstile improves. The electron counting techniques allows us to study nontrivial statistics of Andreev tunneling. In the last part of the thesis, excitations in a superconductor are considered. At low temperatures, the number of excitations of a superconductor should diminish exponentially. However, excess excitations in form of broken Cooper pairs are typically present limiting the performance of superconducting circuits. We discuss ways of probing the excitations in the normal metal - superconductor based structures. We investigate the diffusion of the quasiparticles and their relaxation to normal metallic traps or due to recombination into Cooper pairs via electron-phonon interaction.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Pekola, Jukka, Supervisor, External person
  • Manninen, Antti, Advisor
Award date30 Apr 2014
Place of PublicationEspoo
Publisher
Print ISBNs978-952-6682-10-5
Electronic ISBNs978-952-6682-11-2
Publication statusPublished - 2014
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

theses
metals
excitation
electrons
tunnels
counting
physics
International System of Units
electron phonon interactions
charging
direct current
statistics
traps
costs
atoms
energy

Keywords

  • single-electron transport
  • quantum metrology
  • Andreev tunneling
  • quasiparticle excitations
  • superconductors

Cite this

Maisi, Ville F.. / Andreev tunneling and quasiparticle excitations in mesoscopic normal metal - superconductor structures : Dissertation. Espoo : Centre of Metrology and Accreditation, 2014. 239 p.
@phdthesis{b740fce09b6f4d3387fde28912e214b2,
title = "Andreev tunneling and quasiparticle excitations in mesoscopic normal metal - superconductor structures: Dissertation",
abstract = "Mesoscopic physics deals with systems whose size is between everyday macroscopic scale and the microscopic scale of individual atoms. With mesoscopic structures the flow of single electrons can be controlled. This thesis focuses on the control of single electrons with normal metal - superconductor structures. The emphasis is put on understanding the limitations of the control in the so-called SINIS turnstile, which is a device transporting one electron at a time. By repeating the drive with frequency f, the resulting electrical current in ideal operation I = ef could be utilized as the new definition in the SI unit system. Here e is the elementary charge. In the first part of the thesis, we review the physics of tunnel-coupled normal metals and superconductors and present the operation principle of the SINIS turnstile. We then show parallel operation of ten such devices. This allows one to reach larger currents required for high accuracy measurements. In addition we show that the experimental setup needs to be carefully designed in order to avoid spurious effects due to environmentally assisted tunneling. The second part of the thesis focuses on Andreev tunneling. In this process two electrons tunnel at once in form of a Cooper pair. Andreev tunneling leads to transfer errors, when the tunneling of a single electron is preferred. We discuss the experimental detection techniques of Andreev tunneling based on direct current measurements as well as on electron counting. Furthermore, we show experimentally that by having large enough energy cost for charging the structures, achieved by decreasing the size of the system, Andreev tunneling is suppressed and the accuracy of the turnstile improves. The electron counting techniques allows us to study nontrivial statistics of Andreev tunneling. In the last part of the thesis, excitations in a superconductor are considered. At low temperatures, the number of excitations of a superconductor should diminish exponentially. However, excess excitations in form of broken Cooper pairs are typically present limiting the performance of superconducting circuits. We discuss ways of probing the excitations in the normal metal - superconductor based structures. We investigate the diffusion of the quasiparticles and their relaxation to normal metallic traps or due to recombination into Cooper pairs via electron-phonon interaction.",
keywords = "single-electron transport, quantum metrology, Andreev tunneling, quasiparticle excitations, superconductors",
author = "Maisi, {Ville F.}",
year = "2014",
language = "English",
isbn = "978-952-6682-10-5",
series = "MIKES Publications Doctoral Dissertations",
publisher = "Centre of Metrology and Accreditation",
address = "Finland",
school = "Aalto University",

}

Andreev tunneling and quasiparticle excitations in mesoscopic normal metal - superconductor structures : Dissertation. / Maisi, Ville F.

Espoo : Centre of Metrology and Accreditation, 2014. 239 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Andreev tunneling and quasiparticle excitations in mesoscopic normal metal - superconductor structures

T2 - Dissertation

AU - Maisi, Ville F.

PY - 2014

Y1 - 2014

N2 - Mesoscopic physics deals with systems whose size is between everyday macroscopic scale and the microscopic scale of individual atoms. With mesoscopic structures the flow of single electrons can be controlled. This thesis focuses on the control of single electrons with normal metal - superconductor structures. The emphasis is put on understanding the limitations of the control in the so-called SINIS turnstile, which is a device transporting one electron at a time. By repeating the drive with frequency f, the resulting electrical current in ideal operation I = ef could be utilized as the new definition in the SI unit system. Here e is the elementary charge. In the first part of the thesis, we review the physics of tunnel-coupled normal metals and superconductors and present the operation principle of the SINIS turnstile. We then show parallel operation of ten such devices. This allows one to reach larger currents required for high accuracy measurements. In addition we show that the experimental setup needs to be carefully designed in order to avoid spurious effects due to environmentally assisted tunneling. The second part of the thesis focuses on Andreev tunneling. In this process two electrons tunnel at once in form of a Cooper pair. Andreev tunneling leads to transfer errors, when the tunneling of a single electron is preferred. We discuss the experimental detection techniques of Andreev tunneling based on direct current measurements as well as on electron counting. Furthermore, we show experimentally that by having large enough energy cost for charging the structures, achieved by decreasing the size of the system, Andreev tunneling is suppressed and the accuracy of the turnstile improves. The electron counting techniques allows us to study nontrivial statistics of Andreev tunneling. In the last part of the thesis, excitations in a superconductor are considered. At low temperatures, the number of excitations of a superconductor should diminish exponentially. However, excess excitations in form of broken Cooper pairs are typically present limiting the performance of superconducting circuits. We discuss ways of probing the excitations in the normal metal - superconductor based structures. We investigate the diffusion of the quasiparticles and their relaxation to normal metallic traps or due to recombination into Cooper pairs via electron-phonon interaction.

AB - Mesoscopic physics deals with systems whose size is between everyday macroscopic scale and the microscopic scale of individual atoms. With mesoscopic structures the flow of single electrons can be controlled. This thesis focuses on the control of single electrons with normal metal - superconductor structures. The emphasis is put on understanding the limitations of the control in the so-called SINIS turnstile, which is a device transporting one electron at a time. By repeating the drive with frequency f, the resulting electrical current in ideal operation I = ef could be utilized as the new definition in the SI unit system. Here e is the elementary charge. In the first part of the thesis, we review the physics of tunnel-coupled normal metals and superconductors and present the operation principle of the SINIS turnstile. We then show parallel operation of ten such devices. This allows one to reach larger currents required for high accuracy measurements. In addition we show that the experimental setup needs to be carefully designed in order to avoid spurious effects due to environmentally assisted tunneling. The second part of the thesis focuses on Andreev tunneling. In this process two electrons tunnel at once in form of a Cooper pair. Andreev tunneling leads to transfer errors, when the tunneling of a single electron is preferred. We discuss the experimental detection techniques of Andreev tunneling based on direct current measurements as well as on electron counting. Furthermore, we show experimentally that by having large enough energy cost for charging the structures, achieved by decreasing the size of the system, Andreev tunneling is suppressed and the accuracy of the turnstile improves. The electron counting techniques allows us to study nontrivial statistics of Andreev tunneling. In the last part of the thesis, excitations in a superconductor are considered. At low temperatures, the number of excitations of a superconductor should diminish exponentially. However, excess excitations in form of broken Cooper pairs are typically present limiting the performance of superconducting circuits. We discuss ways of probing the excitations in the normal metal - superconductor based structures. We investigate the diffusion of the quasiparticles and their relaxation to normal metallic traps or due to recombination into Cooper pairs via electron-phonon interaction.

KW - single-electron transport

KW - quantum metrology

KW - Andreev tunneling

KW - quasiparticle excitations

KW - superconductors

M3 - Dissertation

SN - 978-952-6682-10-5

T3 - MIKES Publications Doctoral Dissertations

PB - Centre of Metrology and Accreditation

CY - Espoo

ER -