Reduction of magnetic interlayer coupling in barlowite through isoelectronic substitution

TL;DR

This study uses first-principles calculations to show that isoelectronic substitution of interlayer copper in barlowite reduces magnetic coupling, potentially stabilizing a quantum spin liquid state in the modified material.

Contribution

It demonstrates that selective isoelectronic substitution can effectively weaken interlayer magnetic interactions in barlowite, paving the way for realizing quantum spin liquids.

Findings

Isoelectronic substitution reduces interkagome exchange coupling.

Modified barlowite can be modeled by a simple two-parameter Heisenberg Hamiltonian.

Potential stabilization of quantum spin liquid ground state.

Abstract

Materials with a perfect kagome lattice structure of magnetic ions are intensively sought for, because they may exhibit exotic ground states like the a quantum spin liquid phase. Barlowite is a natural mineral that features perfect kagome layers of copper ions. However, in barlowite there are also copper ions between the kagome layers, which mediate strong interkagome couplings and lead to an ordered ground state. Using {\it ab initio} density functional theory calculations we investigate whether selective isoelectronic substitution of the interlayer copper ions is feasible. After identifying several promising candidates for substitution we calculate the magnetic exchange couplings based on crystal structures predicted from first-principles calculations. We find that isoelectronic substitution with nonmagnetic ions significantly reduces the interkagome exchange coupling. As a consequence, interlayer-substituted barlowite can be described by a simple two-parameter Heisenberg Hamiltonian, for which a quantum spin liquid ground state has been predicted.