Dr. Jernej Mravlje: Effects of Hund's rule coupling on electronic correlations in solids
Povzetek:
Effects of Hund's rule coupling on electronic correlations in solids
Dr. Jernej Mravlje, Institut Jožef Stefan, Ljubljana
When the Coulomb repulsion between electrons in solids becomes larger than the bare electronic scale (the bandwidth), the electronic state is not described well by a Slater determinant of one-electronic states. Electrons in such stronly correlated metals have a dual nature. At high energies, they ressemble the atomic xcitations, at low energies, they behave as an electron gas, with an enhanced mass. Usually, the heavier these excitations (the quasiparticles), the more pronounced is the atomic nature observed at higher energy scales. The ruthenates as well as the recently discovered iron-based superconductors show signatures of correlations in terms of the enhanced electronic mass, but, surprisingly, their spectroscopies do not show pronounced atomic-like features. In the seminar I will present the recent understanding coming from the dynamical mean-field theory that has revealed the key role of the Hund's rule coupling and explained the occurence of electronic correlations at small energy scales that remains invisible to the high-energy spectroscopies [1].
[1] A. Georges, L. de'Medici, and J. Mravlje, Annu. Rev. Cond. Mat. Phys. 4, 137 (2013).
