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dc.contributor.advisorYacoby, Amir
dc.contributor.authorChang, Willy
dc.date.accessioned2014-10-21T19:13:16Z
dc.date.issued2014-10-21
dc.date.submitted2014
dc.identifier.citationChang, Willy. 2014. Superconducting Proximity Effect in InAs Nanowires. Doctoral dissertation, Harvard University.en_US
dc.identifier.otherhttp://dissertations.umi.com/gsas.harvard.inactive:11709en
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:13070025
dc.description.abstractFirst discovered by Holm and Meissner in 1932, the superconducting proximity effect has remained a subject of experimental and theoretical interest. In recent years, it has been proposed that proximity effect in a semiconductor with large g-factor and spin-orbit coupling could lead to exotic phases of superconductivity. This thesis focuses on proximity effect in one of the prime semiconductor candidates -- InAs nanowires. The first set of experiments investigates the superconducting phase-dependent tunneling spectrum of a proximitized InAs quantum dot. We observe tunneling resonances of Andreev bound states in the Kondo regime, and induce quantum phase transitions of the quantum dot ground state with gate voltage and phase bias -- the latter being the first experimental observation of its kind. An additional zero-bias peak of unknown origin is observed to coexist with the Andreev bounds states. The second set of experiments extends upon the first with sharper tunneling resonances and an increase in the device critical field. By applying an external magnetic field, we observe spin-resolved Andreev bound states in proximitized InAs quantum dots. From the linear splitting of the tunneling resonances, we extract g-factors of 5 and 10 in two different devices. The third set of experiments utilizes a novel type of epitaxial core-shell InAs-Al nanowire. We compare the induced gaps of these nanowires with control devices proximitized with evaporated Al films. Our results show that the epitaxial core-shell nanowires possess a much harder induced gap -- up to two orders of magnitude in sub-gap conductance suppression as compared to a factor of five in evaporated control devices. This observation suggests that roughness in S-N interfaces plays a crucial role in the quality of the proximity effect. The fourth set of experiments investigates the gate-tunability of epitaxial half-shell nanowires. In a half-shell nanowire Josephson junction, we measure the normal state resistance, maximum supercurrent, and magnetic field-dependent supercurrent interference patterns. The gate dependences of these independent experimental parameters are consistent with one another and indicate that an InAs nanowire in good ohmic contact to a thin sliver of Al retains its proximity effect and is gate-tunable.en_US
dc.description.sponsorshipPhysicsen_US
dc.language.isoen_USen_US
dash.licenseLAA
dc.subjectPhysicsen_US
dc.subjectInAs nanowiresen_US
dc.subjectProximity effecten_US
dc.subjectSuperconductivityen_US
dc.titleSuperconducting Proximity Effect in InAs Nanowiresen_US
dc.typeThesis or Dissertationen_US
dash.depositing.authorChang, Willy
dc.date.available2014-10-21T19:13:16Z
thesis.degree.date2014en_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.grantorHarvard Universityen_US
thesis.degree.leveldoctoralen_US
thesis.degree.namePh.D.en_US
dc.contributor.committeeMemberMarcus, Charlesen_US
dc.contributor.committeeMemberWestervelt, Roberten_US
dash.contributor.affiliatedChang, Willy


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