Phys. Rev. Lett. 99, 187003 (2007)
NMR Relaxation and Resistivity from Rattling Phonons in Pyrochlore Superconductors
Thomas Dahm1,2 and Kazuo Ueda1
(Received 13 June 2007; published 30 October 2007)
We calculate the temperature dependence of the NMR relaxation rate and electrical resistivity for coupling to a local, strongly anharmonic phonon mode. We argue that the two-phonon Raman process is dominating NMR relaxation. Due to the strong anharmonicity of the phonon an unusual temperature dependence is found having a low temperature peak and becoming constant towards higher temperatures. The electrical resistivity is found to vary like T2 at low temperatures and following a behavior at high temperatures. Both results are in qualitative agreement with recent observations on -pyrochlore oxide superconductors.
Phys. Rev. Lett. 99, 187601 (2007)
Stochastic Dipolar Recoupling in Nuclear Magnetic Resonance of Solids
(Received 1 August 2007; published 2 November 2007)
I describe a nuclear magnetic resonance (NMR) technique, called stochastic dipolar recoupling (SDR), that permits continuous experimental control of the character of spin dynamics between coherent and incoherent limits in a system of magnetic dipole-coupled nuclei. In the fully incoherent limit of SDR, spin polarization transfers occur at distance-dependent rates without the quantum mechanical interferences among pairwise dipole-dipole couplings that often limit the feasibility or precision of structural studies of solids by NMR. In addition to facilitating structural studies, SDR represents a possible route to experimental studies of effects of decoherence on the dynamics of quantum many-body systems.