Occupation resolved conductance of a few electron quantum dot : a test for Kondo correlations in an intermediate coupling regime
department or school: Science, Faculty of
department or school: Physics and Astronomy, Department of
data provider: DSpace
degree campus: UBCV
creator: Drayne, Johann Peter
issued: 2024-04-29T13:43:37Z
issued: 2024
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: The Kondo effect, first discovered in impure bulk metals during the 1930s and explained in the 1960s, has gained significant interest within the field of quantum devices. These devices offer a high degree of tunability and control, enabling rigorous testing of theoretical predictions. Previous studies on the Kondo effect have measured conductance through a quantum dot and observed a zero-bias peak between Coulomb peaks. This effect requires strong coupling between the quantum dot and leads. This work studies a relatively weak coupling, where the characteristic zero-bias peak between Coulomb peaks is not observed. However, as charge degeneracy of the quantum dot is approached, the Kondo temperature increases. This results in a small conductance enhancement at the shoulder of the Coulomb peak. We show that a simultaneous measurement of the quantum dot’s occupation can unveil the small enhancement of conductance due to the Kondo effect. To compare with Numerical Renormalisation Group (NRG) theory, conductance and occupation are measured across a range of temperatures to determine fitting parameters. Good agreement is found at a range of coupling strengths and charge sensor current setpoints. However, a discrepancy is found when the tunnel barriers to the quantum dot are asymmetrically tuned. Strong asymmetric coupling approaches a regime where the quantum dot is coupled to a single lead. A recent measurement of the entropy of a quantum dot coupled to a single lead where Kondo correlations were expected also observed a discrepancy between data and NRG. Interestingly, this work shows that conductance data displays greater Kondo enhancement than NRG, whereas previously measured entropy showed less Kondo enhancement than NRG. A direct comparison of conductance and entropy measured in the same device under similar settings holds promise for illuminating this discrepancy.
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/88046
note: Occupation Resolved Conductance ofa Few Electron Quantum Dot:A Test for Kondo Correlations in an IntermediateCoupling RegimebyJohann Peter DrayneB.Sc., The University of British Columbia, 2022A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES(Physics)THE UNIVERSITY OF BRITISH COLUMBIA(Vancouver)April 2024© Johann Peter Drayne 2024The following individuals certify that they have read, and recommend tothe Faculty of Graduate and Postdoctoral Studies for acceptance, the thesisentitled:Occupation Resolved Conductance of a Few Electron QuantumDot: A Test for Kondo Correlations in an Intermediate CouplingRegimesubmitted by Johann Peter Drayne in partial fulfillment of the require-ments for the degree of Master of Science in Physics.Examining Committee:Joshua Folk, Professor, Physics and Astronomy, UBCSupervisorAlannah Hallas, Assistant Professor, Physics and Astronomy, UBCSupervisory Committee MemberiiAbstractThe Kondo effect, first discovered in impure bulk metals during the 1930sand explained in the 1960s, has gained significant interest within the fieldof quantum devices. These devices offer a high degree of tunability andcontrol, enabling rigorous testing of theoretical predictions. Previous studieson the Kondo effect have measured conductance through a quantum dotand observed a zero-bias peak between Coulomb peaks. This effect requiresstrong coupling between the quantum dot and leads.This work studies a relatively weak coupling, where the characteristiczero-bias peak between Coulomb peaks is not observed. However, as chargedegeneracy of the quantum dot is approached, the Kondo temperature in-creases. This results in a small conductance enhancement at the shoulder ofthe Coulomb peak. We show that a simultaneous measurement of the quan-tum dot’s occupation can unveil the small enhancement of conductance dueto the Kondo effect.To compare with Numerical Renormalisation Group (N…
has type: Thesis/Dissertation
date issued: 2024-05
is shown at: 10.14288/1.0441986
language: eng
degree discipline: Physics
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Folk, Joshua
type: Text
identifier URI: http://hdl.handle.net/2429/88046