Inhomogeneous 1H NMR spin-lattice relaxation in the organic superconductor κ-(BEDT-TTF)2-Cu[N(CN)2]Br

Gezo, Joseph

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https://hdl.handle.net/2142/42132 Copy

Description

Title

Inhomogeneous 1H NMR spin-lattice relaxation in the organic superconductor κ-(BEDT-TTF)2-Cu[N(CN)2]Br

Author(s)

Gezo, Joseph

Issue Date

2013-02-03T19:16:43Z

Director of Research (if dissertation) or Advisor (if thesis)

Giannetta, Russell W.

Doctoral Committee Chair(s)

Weissman, Michael B.

Committee Member(s)

• Giannetta, Russell W.
• Nayfeh, Munir H.
• Stack, John D.

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• magnetic resonance
• organic superconductor
• Nernst effect
• stretched exponential
• spin-lattice relaxation

Abstract

The two-dimensional superconductors based on the organic molecule “ET” have been an active area of research since their discovery over two decades ago. The member of this family with the highest critical temperature, κ-(ET)2Cu[N(CN)2]Br (Tc=11.7 K), has seen renewed interest since the observation of an anomalous Nernst signal by Nam et al in 2007 [51]. A similar effect was seen earlier by Ong’s group in some of the high-temperature cuprate superconductors by [78,84]. This is interpreted to be evidence of a picture of superconductivity in which the resistive transition is driven by thermal fluctuations in the phase of the superconducting order parameter. Below Tc, these fluctuations take the form of bound vortex-antivortex pairs that have no long-range effect on the phase. At Tc, they undergo a Kosterlitz-Thouless unbinding transition; the unbound vortices destroy long-range phase coherence. Previously reported proton NMR measurements on this material have shown a high sensitivity to vortex motion, but reported no interesting behavior above the phase transition [15,25,42]. In this thesis, we revisit the 1H NMR properties of κ-(ET)2Cu[N(CN)2]Br, paying specific attention to the spin-lattice relaxation, to look for some fingerprint of the phenomenon observed by Nam et al.

Graduation Semester

2012-12

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http://hdl.handle.net/2142/42132

Copyright and License Information

Copyright 2012 Joseph Gezo

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