{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/77197"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/77197","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Raman Scattering From the Superconductor Niobium-Diselenide","abstract":"At 33 K 2H-NbSe(,2) distorts into an incommensurate charge density wave (CDW) state. The Raman spectrum shows amplitude modes of A and E symmetry near 40 cm('-1) induced by the CDW. At 7 K this material becomes superconducting, and at 2 K we observe additional Raman peaks near 20 cm('-1), one each of A and E symmetry. These are close in energy to the energy gap 2(DELTA), as measured by far infrared transmission. The Raman activity of the gap excitations is believed to be caused by coupling to the Raman active CDW phonon modes. Such coupling is shown directly by the changes in the Raman spectra at 2 K due to an applied magnetic field. The zero field results can be explained by a model (by C. A. Balseiro and L. M. Falicov) in which the optical CDW phonon modes couple to superconducting electrons, and the resulting phonon self energy is calculated using the BCS theory for the electrons.","abstract_html":"At 33 K 2H-NbSe(,2) distorts into an incommensurate charge density wave (CDW) state. The Raman spectrum shows amplitude modes of A and E symmetry near 40 cm('-1) induced by the CDW. At 7 K this material becomes superconducting, and at 2 K we observe additional Raman peaks near 20 cm('-1), one each of A and E symmetry. These are close in energy to the energy gap 2(DELTA), as measured by far infrared transmission. The Raman activity of the gap excitations is believed to be caused by coupling to the Raman active CDW phonon modes. Such coupling is shown directly by the changes in the Raman spectra at 2 K due to an applied magnetic field. The zero field results can be explained by a model (by C. A. Balseiro and L. M. Falicov) in which the optical CDW phonon modes couple to superconducting electrons, and the resulting phonon self energy is calculated using the BCS theory for the electrons.","abstract_has_math":false,"creators":["Sooryakumar, Ratnasingham"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-05-13T15:22:23Z","date_published":"2015-05-13T15:22:23Z","updated_at":"2026-07-22T22:26:10Z","subjects":["Physics, Condensed Matter"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8108670"],"render_values":[{"text":"(UMI)AAI8108670","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/77197","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Sooryakumar, Ratnasingham"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-05-13T15:22:23Z","10000-01-01","1980"]},{"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, Condensed Matter"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/77197","(UMI)AAI8108670"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["At 33 K 2H-NbSe(,2) distorts into an incommensurate charge density wave (CDW) state. The Raman spectrum shows amplitude modes of A and E symmetry near 40 cm('-1) induced by the CDW. At 7 K this material becomes superconducting, and at 2 K we observe additional Raman peaks near 20 cm('-1), one each of A and E symmetry. These are close in energy to the energy gap 2(DELTA), as measured by far infrared transmission. The Raman activity of the gap excitations is believed to be caused by coupling to the Raman active CDW phonon modes. Such coupling is shown directly by the changes in the Raman spectra at 2 K due to an applied magnetic field. The zero field results can be explained by a model (by C. A. Balseiro and L. M. Falicov) in which the optical CDW phonon modes couple to superconducting electrons, and the resulting phonon self energy is calculated using the BCS theory for the electrons.","Extensions of the zero field theory to include lifetime broadening effects and consequences of changing the electron-phonon coupling are presented. The results in an external magnetic field are explained in terms of a complex gap parameter.","These results are confirmed by experiments on samples of 2H-NbSe(,2) that have their CDW transition suppressed by non-magnetic impurities but still retain their superconducting properties.","Made available in DSpace on 2015-05-13T15:22:23Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8108670.PDF: 3884184 bytes, checksum: a402cee102f95f380d491997c86af66b (MD5) Previous issue date: 1980","Embargo set by: Seth Robbins for item 78408 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","164 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980."]},{"key":"dc:title","label":"Title","values":["Raman Scattering From the Superconductor Niobium-Diselenide"]}]}],"canonical_facts":{"dc:creator":["Sooryakumar, Ratnasingham"],"dc:date":["2015-05-13T15:22:23Z","10000-01-01","1980"],"dc:description":["At 33 K 2H-NbSe(,2) distorts into an incommensurate charge density wave (CDW) state. The Raman spectrum shows amplitude modes of A and E symmetry near 40 cm('-1) induced by the CDW. At 7 K this material becomes superconducting, and at 2 K we observe additional Raman peaks near 20 cm('-1), one each of A and E symmetry. These are close in energy to the energy gap 2(DELTA), as measured by far infrared transmission. The Raman activity of the gap excitations is believed to be caused by coupling to the Raman active CDW phonon modes. Such coupling is shown directly by the changes in the Raman spectra at 2 K due to an applied magnetic field. The zero field results can be explained by a model (by C. A. Balseiro and L. M. Falicov) in which the optical CDW phonon modes couple to superconducting electrons, and the resulting phonon self energy is calculated using the BCS theory for the electrons.","Extensions of the zero field theory to include lifetime broadening effects and consequences of changing the electron-phonon coupling are presented. The results in an external magnetic field are explained in terms of a complex gap parameter.","These results are confirmed by experiments on samples of 2H-NbSe(,2) that have their CDW transition suppressed by non-magnetic impurities but still retain their superconducting properties.","Made available in DSpace on 2015-05-13T15:22:23Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8108670.PDF: 3884184 bytes, checksum: a402cee102f95f380d491997c86af66b (MD5) Previous issue date: 1980","Embargo set by: Seth Robbins for item 78408 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","164 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980."],"dc:identifier":["http://hdl.handle.net/2142/77197","(UMI)AAI8108670"],"dc:language":["eng"],"dc:subject":["Physics, Condensed Matter"],"dc:title":["Raman Scattering From the Superconductor Niobium-Diselenide"],"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":"2026-07-22T22:26:10Z"}