{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/95263"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/95263","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Tunable spin polarization and conductance anomalies in mesoscopic one-dimensional systems","abstract":"The electronic transport properties of mesoscopic one-dimensional (1D) devices have attracted significant interest because of their potential applications and their unique characteristics, some of which – for instance, the “0.7” conductance anomaly in quantum point contacts – have remained unexplained. In this dissertation, we present a comprehensive theoretical model for electronic transport in quasi-1D systems, accounting for many-body effects and neglecting spin–orbit couplings. Then, with this model, we predict that 1D systems can sustain a hierarchy of spin-polarized configurations which emerge above a carrier concentration threshold and are responsible for the 0.7 anomaly. The basis of our theory is an unrestricted three-dimensional Hartree-Fock approach that incorporates the effects of confinement strength, applied magnetic field and temperature. We demonstrate that the spin-polarized states are present in the quantum wire even if no magnetic field is present, provided that the electron concentration in the system is above a confinement-dependent threshold. Our subsequent study of ballistic transport in a quantum point contact reveals that the 0.7 anomaly appears at the threshold concentration for polarization, at a conductance value that is insensitive to temperature due to the capacitive effect exerted by the gates, even though the anomalous shoulder becomes wider with increasing temperature. The 0.7 anomaly is accompanied by another “kink” at ~0.3G0, which results from the singularity of the 1D density of states and disappears with rising temperatures. Our results provide an explanation for the experimental features of the conductance anomaly and underscore the importance of treating the confinement potential in the quasi-1D constriction as three-dimensional.","abstract_html":"The electronic transport properties of mesoscopic one-dimensional (1D) devices have attracted significant interest because of their potential applications and their unique characteristics, some of which – for instance, the “0.7” conductance anomaly in quantum point contacts – have remained unexplained. In this dissertation, we present a comprehensive theoretical model for electronic transport in quasi-1D systems, accounting for many-body effects and neglecting spin–orbit couplings. Then, with this model, we predict that 1D systems can sustain a hierarchy of spin-polarized configurations which emerge above a carrier concentration threshold and are responsible for the 0.7 anomaly. The basis of our theory is an unrestricted three-dimensional Hartree-Fock approach that incorporates the effects of confinement strength, applied magnetic field and temperature. We demonstrate that the spin-polarized states are present in the quantum wire even if no magnetic field is present, provided that the electron concentration in the system is above a confinement-dependent threshold. Our subsequent study of ballistic transport in a quantum point contact reveals that the 0.7 anomaly appears at the threshold concentration for polarization, at a conductance value that is insensitive to temperature due to the capacitive effect exerted by the gates, even though the anomalous shoulder becomes wider with increasing temperature. The 0.7 anomaly is accompanied by another “kink” at ~0.3G0, which results from the singularity of the 1D density of states and disappears with rising temperatures. Our results provide an explanation for the experimental features of the conductance anomaly and underscore the importance of treating the confinement potential in the quasi-1D constriction as three-dimensional.","abstract_has_math":false,"creators":["Sanchez, Alfredo Xavier"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Leburton, Jean-Pierre","Ryu, Shinsei","Mason, Nadya","Peng, Jen-Chieh"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017-03-01T15:45:51Z","date_published":"2017-03-01T15:45:51Z","updated_at":"2026-07-22T22:26:35Z","subjects":["quantum point contacts","nanoelectronics","mesoscopic physics","spin polarization","spintronics"],"languages":["en"],"rights":["© 2016 Alfredo X. 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The basis of our theory is an unrestricted three-dimensional Hartree-Fock approach that incorporates the effects of confinement strength, applied magnetic field and temperature. We demonstrate that the spin-polarized states are present in the quantum wire even if no magnetic field is present, provided that the electron concentration in the system is above a confinement-dependent threshold. Our subsequent study of ballistic transport in a quantum point contact reveals that the 0.7 anomaly appears at the threshold concentration for polarization, at a conductance value that is insensitive to temperature due to the capacitive effect exerted by the gates, even though the anomalous shoulder becomes wider with increasing temperature. The 0.7 anomaly is accompanied by another “kink” at ~0.3G0, which results from the singularity of the 1D density of states and disappears with rising temperatures. Our results provide an explanation for the experimental features of the conductance anomaly and underscore the importance of treating the confinement potential in the quasi-1D constriction as three-dimensional.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-02-28 without embargo terms","The student, Alfredo Sanchez, accepted the attached license on 2016-08-19 at 10:00.","The student, Alfredo Sanchez, submitted this Dissertation for approval on 2016-08-19 at 10:01.","This Dissertation was approved for publication on 2016-08-23 at 13:53.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10119 on 2017-02-28 at 14:45:18","Made available in DSpace on 2017-03-01T15:45:51Z (GMT). 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In this dissertation, we present a comprehensive theoretical model for electronic transport in quasi-1D systems, accounting for many-body effects and neglecting spin–orbit couplings. Then, with this model, we predict that 1D systems can sustain a hierarchy of spin-polarized configurations which emerge above a carrier concentration threshold and are responsible for the 0.7 anomaly. The basis of our theory is an unrestricted three-dimensional Hartree-Fock approach that incorporates the effects of confinement strength, applied magnetic field and temperature. We demonstrate that the spin-polarized states are present in the quantum wire even if no magnetic field is present, provided that the electron concentration in the system is above a confinement-dependent threshold. Our subsequent study of ballistic transport in a quantum point contact reveals that the 0.7 anomaly appears at the threshold concentration for polarization, at a conductance value that is insensitive to temperature due to the capacitive effect exerted by the gates, even though the anomalous shoulder becomes wider with increasing temperature. The 0.7 anomaly is accompanied by another “kink” at ~0.3G0, which results from the singularity of the 1D density of states and disappears with rising temperatures. Our results provide an explanation for the experimental features of the conductance anomaly and underscore the importance of treating the confinement potential in the quasi-1D constriction as three-dimensional.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-02-28 without embargo terms","The student, Alfredo Sanchez, accepted the attached license on 2016-08-19 at 10:00.","The student, Alfredo Sanchez, submitted this Dissertation for approval on 2016-08-19 at 10:01.","This Dissertation was approved for publication on 2016-08-23 at 13:53.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10119 on 2017-02-28 at 14:45:18","Made available in DSpace on 2017-03-01T15:45:51Z (GMT). No. of bitstreams: 3 SANCHEZ-DISSERTATION-2016.pdf: 3166994 bytes, checksum: 7f0a4e693b1af466fe0508e4779bb5ba (MD5) LICENSE.txt: 4212 bytes, checksum: a5911988769c54dfdcc9b7adb698f971 (MD5) PROQUEST_LICENSE.txt: 4558 bytes, checksum: 8c55bf119183e8f9876b37b058b36000 (MD5) Previous issue date: 2016-08-23"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/95263"],"dc:language":["en"],"dc:rights":["© 2016 Alfredo X. Sánchez"],"dc:subject":["quantum point contacts","nanoelectronics","mesoscopic physics","spin polarization","spintronics"],"dc:title":["Tunable spin polarization and conductance anomalies in mesoscopic one-dimensional systems"],"dc:type":["text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:35Z"}