DQMP - Informal Seminar - 19.07.2024 - 11:00 - Carolina de Almeida Marques

19.07.2024 11:00 – 12:00

A short story of quasiparticle interference
Carolina de Almeida Marques
Department of Physics, University of Zurich,

The observation that a material is metallic, insulating, superconducting or is magnetic is intrinsically related to the dispersion of its electronic states across the Fermi level and the shape of the Fermi surface. The electronic structure is determined by an intricate relationship between the symmetry of the atomic lattice, the Coulomb repulsion, electron-phonon coupling, exchange splitting and spin-orbit coupling. The interplay between these mechanisms results in the rich phase diagrams found in strongly correlated materials, with examples including the cuprate, iron-based and heavy fermion superconductors. To enable a controlled manipulation of the electronic states of these materials to induce desired electronic properties, it is thus necessary to know how the different underlying microscopic mechanisms affect the electronic structure and how to tune them.
In this talk, I will discuss how to study the electronic structure using quasiparticle interference (QPI) measured in scanning tunnelling microscopy (STM). In QPI, the electronic dispersion in momentum space can be measured indirectly due to the scattering of quasiparticles by an object breaking translation symmetry. These create standing waves in the local density of states in real space, which can be imaged in STM as a function of energy across the Fermi level. By taking the Fourier transform of these images, the scattering patterns in momentum space can be accessed and the dispersion relation obtained. In a single band system, the relationship between the momentum space and the scattering vectors is trivial, however, it can become quite complicated for multiband systems, as well as when spin-orbit coupling and electronic correlations play a significant role. I will present our QPI measurements on a three-dimensional system as well as on three members of the Ruddlesden-Popper series of the strontium ruthenates. These, together with continuum local density of states calculations, allow to illustrate the role of microscopic mechanisms in the electronic structure of correlated electron materials, such as the three-dimensionality of the band structure, wavefunction overlap and spin-orbit coupling.


Organisé par Árpád Pásztor

Lieu

Bâtiment: Ecole de Physique

Salle MaNEP

entrée libre