Quan Yin

Phonons and Electron-Phonon Interactions For the calculation of phonon spectra we used density functional linear response approach implemented using LMTO basis [1, 3], which has successfully produced the lattice dynamics of solids [4] including actinides materials such as plutonium [9] and UO2 [7]. The spin–orbit coupling effect is included in this calculation. A q–grid of 6×6×6 is used to compute phonon frequencies, which generates 36 irreducible q points in the Brillouin zone. The phonon dispersion of UN along 3 high–symmetry directions is plotted in Fig. 1(a) together with experimental data measured by neutron scattering [10]. As shown in Fig. 1(b), UC carries similar phonon dispersions but slightly lower phonon energies. Despite apparent presence of correlation effects, excellent agreement is achieved with the local density approximation (LDA). Similar success of LDA in studying lattice dynamics of strongly correlated metallic systems have been reported earlier, for example in Palladium [4], high temperature superconducting cuprates [5], and recently iron pnictides [6]. Calculations of electron–phonon interactions and transport properties require, on the other hand, quasiparticle description of the one–electron spectra when evaluating Eliashberg and transport spectral functions by integrating over the Fermi surfaces [4]. As a result, due to large mass enhancement, the straightforward LDA procedure can produce wrong electron–phonon resistivities which was indeed found in our calculation for UC where ρ(T )EPI was overestimated by a factor of 3 compared to experiment. This is despite of simple arguments that would suggest that any multiplicative effects on the electron mass renormalization should cancel out in the resistivity, because it enters both the scattering rate τ that appears in the denominator, and the electronic mass that appears in the numerator of the expression for ρ(T )EPI , which is evident from a simple Drude formula for ρ = m/(neτ). However, in general, this does not apply to multi–band systems where only correlated f– electron wave functions are primarily affected by strong Coulomb interactions. In order to evaluate the electron–phonon scattering in the presence of correlations we develop a method that accounts for the effects from quasiparticle mass renormalizations and spectral weight transfer by utilizing interacting Green functions. We have previously shown [8] 0.0 0.5 1.0 0 2 4 6 8 10 12 14