{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/23160"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/23160","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Quasiparticle bound states in normal metal/superconductor structures probed by scanning tunneling microscopy","abstract":"In this work we consider systems in which small normal-metal structures (N) are put into contact with a large superconductor (S), with the goal of spatially characterizing the superconductivity. Confined regions with suppressed superconductivity will support quasiparticle bound states, which can be measured spectroscopically. Using a custom-built cryogenic scanning tunneling microscopy system, we have probed the bound states of an NS system consisting of Au (N) droplets of nanometer dimensions in electrical contact with bulk NbSe$\\sb 2$ (S). A quasiparticle bound state was observed even when tunneling directly into the NbSe$\\sb 2$, clear evidence for a significant reduction of the superconductivity inside the NbSe$\\sb 2$ induced by the proximity of the Au over-layer. By invoking a proximity effect model, we are able to characterize the vertical and lateral variation of the pair potential $\\Delta$ inside the superconductor. We find that a severe suppression occurs which is beyond the conventional theory. We believe that this effect arises from the short coherence length of the superconductor, so that the spatial variation of the interaction parameter g becomes important. The profile of $\\Delta$ that we extract from our data then combines both the conventional proximity suppression of $\\Delta$ and its modulation by the profile of g, representing the first observation of spatial structure of the interaction parameter.","abstract_html":"In this work we consider systems in which small normal-metal structures (N) are put into contact with a large superconductor (S), with the goal of spatially characterizing the superconductivity. Confined regions with suppressed superconductivity will support quasiparticle bound states, which can be measured spectroscopically. Using a custom-built cryogenic scanning tunneling microscopy system, we have probed the bound states of an NS system consisting of Au (N) droplets of nanometer dimensions in electrical contact with bulk NbSe$\\sb 2$ (S). A quasiparticle bound state was observed even when tunneling directly into the NbSe$\\sb 2$, clear evidence for a significant reduction of the superconductivity inside the NbSe$\\sb 2$ induced by the proximity of the Au over-layer. By invoking a proximity effect model, we are able to characterize the vertical and lateral variation of the pair potential $\\Delta$ inside the superconductor. We find that a severe suppression occurs which is beyond the conventional theory. We believe that this effect arises from the short coherence length of the superconductor, so that the spatial variation of the interaction parameter g becomes important. The profile of $\\Delta$ that we extract from our data then combines both the conventional proximity suppression of $\\Delta$ and its modulation by the profile of g, representing the first observation of spatial structure of the interaction parameter.","abstract_has_math":true,"creators":["Tessmer, Stuart Holden"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Van Harlingen, Dale J."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T14:04:18Z","date_published":"2011-05-07T14:04:18Z","updated_at":"2026-07-22T22:25:21Z","subjects":["Physics, Electricity and Magnetism","Physics, Condensed Matter"],"languages":["eng"],"rights":["Copyright 1995 Tessmer, Stuart Holden"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9624511","(UMI)AAI9624511"],"render_values":[{"text":"AAI9624511","href":null,"code":true},{"text":"(UMI)AAI9624511","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/23160","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Van Harlingen, Dale J."]},{"key":"dc:creator","label":"Author","values":["Tessmer, Stuart Holden"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T14:04:18Z","10000-01-01","1995"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics, Electricity and Magnetism","Physics, Condensed Matter"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1995 Tessmer, Stuart Holden"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9624511","(UMI)AAI9624511","http://hdl.handle.net/2142/23160"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["In this work we consider systems in which small normal-metal structures (N) are put into contact with a large superconductor (S), with the goal of spatially characterizing the superconductivity. Confined regions with suppressed superconductivity will support quasiparticle bound states, which can be measured spectroscopically. Using a custom-built cryogenic scanning tunneling microscopy system, we have probed the bound states of an NS system consisting of Au (N) droplets of nanometer dimensions in electrical contact with bulk NbSe$\\sb 2$ (S). A quasiparticle bound state was observed even when tunneling directly into the NbSe$\\sb 2$, clear evidence for a significant reduction of the superconductivity inside the NbSe$\\sb 2$ induced by the proximity of the Au over-layer. By invoking a proximity effect model, we are able to characterize the vertical and lateral variation of the pair potential $\\Delta$ inside the superconductor. We find that a severe suppression occurs which is beyond the conventional theory. We believe that this effect arises from the short coherence length of the superconductor, so that the spatial variation of the interaction parameter g becomes important. The profile of $\\Delta$ that we extract from our data then combines both the conventional proximity suppression of $\\Delta$ and its modulation by the profile of g, representing the first observation of spatial structure of the interaction parameter.","Made available in DSpace on 2011-05-07T14:04:18Z (GMT). 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Confined regions with suppressed superconductivity will support quasiparticle bound states, which can be measured spectroscopically. Using a custom-built cryogenic scanning tunneling microscopy system, we have probed the bound states of an NS system consisting of Au (N) droplets of nanometer dimensions in electrical contact with bulk NbSe$\\sb 2$ (S). A quasiparticle bound state was observed even when tunneling directly into the NbSe$\\sb 2$, clear evidence for a significant reduction of the superconductivity inside the NbSe$\\sb 2$ induced by the proximity of the Au over-layer. By invoking a proximity effect model, we are able to characterize the vertical and lateral variation of the pair potential $\\Delta$ inside the superconductor. We find that a severe suppression occurs which is beyond the conventional theory. We believe that this effect arises from the short coherence length of the superconductor, so that the spatial variation of the interaction parameter g becomes important. The profile of $\\Delta$ that we extract from our data then combines both the conventional proximity suppression of $\\Delta$ and its modulation by the profile of g, representing the first observation of spatial structure of the interaction parameter.","Made available in DSpace on 2011-05-07T14:04:18Z (GMT). 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