Electronic properties of alkali-metal loaded zeolites -- a "supercrystal" Mott insulator

TL;DR

This study uses first-principles calculations to reveal that alkali-metal loaded zeolites form a supercrystal Mott insulator with strongly correlated electrons, offering new insights into their electronic and magnetic properties.

Contribution

The paper introduces the concept of a supercrystal formed by guest atoms in zeolites and demonstrates their Mott-insulating behavior using dynamical mean-field theory.

Findings

System exhibits a simple band structure with superatom orbitals.

Coulomb and exchange energies indicate strong electron correlations.

System is predicted to be a Mott insulator near a ferromagnetic phase.

Abstract

First-principles band calculations are performed for the first time for an open-structured zeolite (LTA) with guest atoms (potassium) introduced in their cages. A surprisingly simple band structure emerges, which indicates that this system may be regarded as a "supercrystal", where each cluster of guest atoms with diameter $\sim$10\AA acts as a "superatom" with well-defined $s$- and $p$-like orbitals, which in turn form the bands around the Fermi energy. The calculated Coulomb and exchange energies for these states turn out to be in the strongly-correlated regime. With the dynamical mean-field theory we show the system should be on the Mott-insulator side, and, on a magnetic phase diagram for degenerate-orbital systems, around the ferromagnetic regime, in accord with experimental results. We envisage this class of systems can provide a new avenue for materials design.