Seminars Archive

Band-selected Fermi-surface shrinking driven by many-body interactions: theory and experiments

Abstract
Dynamical effects of retarded boson-mediated electron-electron interactions (phonons, spin fluctuations, ...) are relevant in a wide range of materials. Most common is the renormalization of the Fermi velocity, which gives rise to the well-known "kink" feature in the electronic dispersion observed in ARPES measurements. Also predicted, but more elusive, is a upwards/downwards shift of the electronic band, reflected in a shrinking/expansion of the Fermi surface. In common systems this effect is compensated by a corresponding shift of the Fermi level in order to conserve the total charge density. In this talk I will present few examples where the a selective band shift can be actually observed and controlled, with a corresponding Fermi surface shinking/expansion. I will discuss the case of iron-based superconductors, where such Fermi surface shrinking has been observed by means of de Haas-van Alphen and ARPES experiments, and the case of MgB2, where a Fermi surface expansion, mediated by hot phonons, can be induced and observed in time resolved pump-probe optics.