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Jernej Mravlje - Centre de Physique Théorique (CPHT), École Polytechnique, Palaiseau

The coherence-incoherence crossover and mass-renormalization puzzles in Sr2RuO4

In Sr2RuO4 the crossover from a Fermi liquid to an incoherent regime is observed at a low temperature of order 50K. In the seminar I will address two questions, which remained unresolved until now : (i) Why is the coherence scale in this relatively wide-band material so low ? and (ii) Why does the widest band counter-intuitively exhibit largest mass enhancement ? The solution to these puzzles, which we obtained using electronic structure calculations with correlations taken into account within dynamical mean-field theory (i.e. within LDA+DMFT framework), relies on the importance of Hund’s rule and the proximity of the van Hove singularity to the Fermi surface in the broadest band. The former is relevant to all materials in which on-site interaction (Hubbard U) is screened more than the multiplet interactions (e.g. 4-d transition metal oxides). The latter is relevant to all materials with enhanced density of states close to the Fermi surface (e.g. layered materials at a certain filling). Sr2RuO4, when looked at with the lens of modern theoretical tools, is thus revealing a secret about a coherence-incoherence crossover in a wide class of materials.


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