IQIM Postdoctoral and Graduate Student Seminar

Friday October 9, 2015 4:00 PM

Superconductivity in Uranium and Plutonium revealed by NMR

Speaker: Andrew Mounce, Los Alamos National Labs/Sandia Labs
Location: East Bridge 114

Abstract: The discovery of f electron superconductivity in CeCu2Si2 [1] and UPt3 [2] revolutionized the way we think about superconductivity, even before the discovery of high temperature superconducting cuprates [3]. The superconducting state in these materials cannot be described by the Bardeen-Cooper-Schrieffer model of phonon mediated superconductivity. [4] Furthermore, the superconducting state is established from a strongly correlated quasiparticle state where correlations between conduction and localized electrons create quasiparticles with mass 100's of times larger than a typical conduction electron. Nuclear magnetic resonance (NMR) is a unique probe in that it is both microscopic, giving information about local properties at the nuclear site, and bulk, averaging these properties over an ensemble of equivalent crystal sites. Through NMR measurements, clues about the superconducting electronic paring symmetry, orbital angular momentum, and magnetic fluctuations are revealed. In this presentation, I will describe unconventional heavy fermion superconductivity and the NMR probe of materials. Building on this foundation, I will demonstrate how NMR has been utilized at Los Alamos to uncover the details of superconductivity in a Uranium superconductor U2PtC2 [5] and the Plutonium superconductor family, the so-called Pu-115's. [6]

 

[1] Steglich, F et al. Phys. Rev. Lett. 43, 1892 (1979).

[2] Stewart, G. R. et al. Phys. Rev. Lett. 52, 679 (1984).

[3] Bednorz, J. G. and Muller, K. A. Z. Phys. B. Con. Mat. 64, 189 (1986).

[4] Bardeen, J. Cooper, L. N. and Schrie_er, J. R. Phys. Rev. 106, 162 (1957).

[5] Mounce, A. M. et al. Phys. Rev. Lett. 114, 127001 (2015).

[6] Koutroulakis, G et al. APS Meeting Abstracts 1, 46013 (2014).


 

 

Series IQIM Postdoctoral and Graduate Student Seminar Series

Contact: Marcia Brown at 626-395-4013 marciab@caltech.edu