# High-spin to low-spin and orbital polarization transitions in multiorbital Mott systems

## TL;DR

This paper investigates how crystal field splitting and Hund coupling influence phase transitions in a two-orbital Mott system, revealing novel insulating states and orbital selectivity through advanced dynamical mean field theory.

## Contribution

It introduces a detailed study of phase boundaries and orbital polarization transitions in multiorbital systems using a new impurity solver at strong coupling and low temperatures.

## Key findings

- Hund coupling induces a novel Mott insulating phase with zero orbital susceptibility.
- Crystal field splitting can lead to orbital selective Mott states away from half-filling.
- Phase diagrams as functions of Coulomb repulsion, exchange coupling, and crystal field splitting are mapped.

## Abstract

We study the interplay of crystal field splitting and Hund coupling in a two-orbital model which captures the essential physics of systems with two electrons or holes in the e_g shell. We use single site dynamical mean field theory with a recently developed impurity solver which is able to access strong couplings and low temperatures. The fillings of the orbitals and the location of phase boundaries are computed as a function of Coulomb repulsion, exchange coupling and crystal field splitting. We find that the Hund coupling can drive the system into a novel Mott insulating phase with vanishing orbital susceptibility. Away from half-filling, the crystal field splitting can induce an orbital selective Mott state.