Coherent Band Excitations in CePd₃

A crossover from coherent quasiparticle bands at low temperature to incoherent electronic fluctuations at high temperature is a hallmark of strongly correlated electron systems, ranging from heavy fermions to high temperature superconductors. Realistic calculations that combine Density Functional Theory with Dynamical Mean Field Theory (DFT+DMFT) in order to incorporate both local correlations and itinerant bands predict a gradual loss of quasiparticle spectral weight at the Fermi energy with increasing temperature, but comparisons with spectroscopic data have been limited. For example, in cerium compounds, many of the relevant electronic states are unoccupied and therefore inaccessible to ARPES measurements. However, recent instrumental advances at spallation neutron sources allow inelastic neutron scattering (INS) to be used as an alternative probe of quasiparticle coherence. The dynamic magnetic susceptibility, Im χ(Q,ω), is proportional to the joint electronic density-of-states, amplified by particle-hole interactions. I will present the results of a comparison of four-dimensional INS data, measured over a large (Q,ω)-volume on a single crystal of CePd₃, with DFT+DMFT calculations.¹ The formation of coherent f-electron bands at low temperature produces modulations of intensity throughout the Brillouin zone, which are suppressed with increasing temperature. The agreement between experiment and theory on an absolute scale shows that we have a robust first-principles understanding of the temperature dependence of f-electron coherence.
1. E.A. Goremychkin, H. Park, R. Osborn, S. Rosenkranz, J.P. Castellan, V.R. Fanelli, A.D. Christianson, M.B. Stone, E.D. Bauer, K.J. McClellan, D.D. Byler, and J.M. Lawrence, Science (in press).