Spin, charge, and orbital correlations in the one-dimensional t2g-orbital Hubbard model

TL;DR

This paper maps the phase diagram of a one-dimensional t2g-orbital Hubbard model, revealing phase transitions between paramagnetic insulators, ferromagnetic states, and metallic regimes influenced by electron density and Hund's coupling.

Contribution

It provides the first detailed phase diagram of the 1D t2g-orbital Hubbard model using DMRG and Lanczos methods, highlighting phase transitions relevant for Co-based compounds.

Findings

First-order transition between PM insulator and FM state at n=5

Transition from PM insulator to metal with doping

Robustness of magnetic states across parameters

Abstract

We present the zero-temperature phase diagram of the one-dimensional t2g-orbital Hubbard model, obtained using the density-matrix renormalization group and Lanczos techniques. Emphasis is given to the case for the electron density n=5 corresponding to five electrons per site, of relevance for some Co-based compounds. However, several other cases for electron densities between n=3 and 6 are also studied. At n=5, our results indicate a first-order transition between a paramagnetic (PM) insulator phase and a fully-polarized ferromagnetic (FM) state by tuning the Hund's coupling. The results also suggest a transition from the n=5 PM insulator phase to a metallic regime by changing the electron density, either via hole or electron doping. The behavior of the spin, charge, and orbital correlation functions in the FM and PM states are also described in the text and discussed. The robustness of these two states varying parameters suggests that they may be of relevance in more realistic higher dimensional systems as well.