Magnetism, electronic transport, and disorder in strongly correlated systems

TL;DR

This thesis explores how strong electronic correlations influence magnetism, spectral properties, and transport in models like the Hubbard model, revealing new mechanisms and interpretations relevant for complex materials and disordered systems.

Contribution

It introduces a correlation-driven mechanism for spin-polarized transport and applies these ideas to materials with strong spin-orbit coupling and disordered nanoparticle systems.

Findings

Identification of local electronic correlations shaping spectral and transport responses.

Discovery of a correlation-driven mechanism for spin-polarized charge transport in antiferromagnets.

Unified interpretation of metal-insulator transitions in complex correlated systems.

Abstract

This thesis investigates the magnetic, spectral, and transport properties of strongly correlated electronic systems, with a primary focus on the Hubbard model and its extensions relevant for real materials. Within the dynamical mean-field theory (DMFT) framework, different regimes of interaction strength, temperature, doping, and magnetic field are explored, highlighting the central role of local electronic correlations in shaping spectral reconstruction and nontrivial transport responses. For the antiferromagnetic Hubbard model under a Zeeman field, magnetoresistance and local metamagnetism are characterized, revealing the coexistence of distinct energy scales associated with charge and spin degrees of freedom. A minimal, purely correlation-driven mechanism for generating spin-polarized charge transport in structurally conventional collinear antiferromagnets is identified, controlled by the simultaneous breaking of particle--hole symmetry and antiferromagnetic sublattice equivalence. Finally, these concepts are applied to correlated materials with strong spin--orbit coupling, such as Sr$_2$IrO$_4$ and Sr$_3$Ir$_2$O$_7$, and to nanoparticle solids dominated by Coulomb blockade and disorder. The results show how ideas developed in correlated lattice models provide a unified interpretation of metal--insulator transitions and spectral reconstruction in complex systems.