Mott transition in Modulated Lattices and Parent Insulator of (K,Tl)yFexSe2 Superconductors

TL;DR

This paper investigates how ordered iron vacancies in modulated lattices induce a Mott transition, explaining the insulating behavior of parent compounds in certain iron-based superconductors through a band-narrowing mechanism.

Contribution

It demonstrates that vacancy ordering causes band-narrowing, pushing the system toward a Mott insulator state, providing insight into the insulating nature of (K,Tl)yFexSe2 parent compounds.

Findings

Ordered vacancies lead to band-narrowing.

Vacancy-induced band-narrowing drives Mott transition.

Explains insulating behavior in parent superconductors.

Abstract

The degree of electron correlations remains a central issue in the iron-based superconductors. The parent iron pnictides are antiferromagnetic, and their bad-metal behavior has been interpreted in terms of proximity to a Mott transition. We study such a transition in multi-orbital models on modulated lattices containing an ordered pattern of iron vacancies, using a slave-rotor method. We show that the ordered vacancies lead to a band-narrowing, which pushes the system to the Mott insulator side. This effect is proposed to underlie the insulating behavior observed in the parent compounds of the newly discovered (K,Tl)yFexSe2 superconductors.