Multiband effects on the conductivity for a multiband Hubbard model

TL;DR

This paper investigates how multiband effects influence electrical conductivity in a one-dimensional two-band Hubbard model, revealing the role of orbital degrees of freedom in metal-insulator transitions relevant to iron-based superconductors.

Contribution

It provides an exact solution-based analysis of multiband effects on conductivity, highlighting the impact of orbital degrees of freedom on the critical interaction strength.

Findings

Orbital degrees of freedom can increase the critical U for metal-insulator transition.

Undoped high-Tc superconductors are insulators, while iron-based superconductors are metals due to multiband effects.

Orbital effects are crucial in understanding the electronic properties of these materials.

Abstract

The newly discovered iron-based superconductors have attracted lots of interests, and the corresponding theoretical studies suggest that the system should have six bands. In this paper, we study the multiband effects on the conductivity based on the exact solutions of one-dimensional two-band Hubbard model. We find that the orbital degree of freedom might enhance the critical value $U_c$ of on-site interaction of the transition from a metal to an insulator. This observation is helpful to understand why undoped High-$T_c$ superconductors are usually insulators, while recently discovered iron-based superconductors are metal. Our results imply that the orbital degree of freedom in the latter cases might play an essential role.