Quantum spin liquid and cluster Mott insulator phases in the Mo3O8 magnets

Abstract

We unveil the microscopic origin of largely debated magnetism in the Mo3O8 quantum systems. Upon considering an extended Hubbard model at 1/6 filling on the anisotropic kagomé lattice formed by the Mo atoms, we argue that its ground state is determined by the competition between kinetic energy and intersite Coulomb interactions, which is controlled by the trimerisation of the kagomé lattice into the Mo3O13 clusters, and the sign of hopping parameters, specifying the electron localisation at such clusters. Based on first-principles calculations, we show that the strong interaction limit reveals a plaquette charge order with unpaired spins at the resonating hexagons that can be realised in LiZn2Mo3O8, and whose origin is solely related to the opposite signs of intracluster and intercluster hoppings, in contrast to all previous scenarios. On the other hand, both Li2InMo3O8 and Li2ScMo3O8 are demonstrated to fall into the weak interaction limit where the electrons are well localised at the Mo3O13 clusters. While the former is found to exhibit long-range antiferromagnetic order, the latter is more likely to reveal short-range order with quantum spin liquid-like excitations. Our results not only reproduce most of the experimentally observed features of the Mo3O8 systems, but will also help to describe various properties in other quantum cluster magnets.

Electrochemical Control of Magnetism on the Breathing Kagome Network of LixScMo3O8

“…It has been postulated that the magnetic behavior may show features of a resonating valence-bond state, 22,23 dimerization, 24 or plaquette charge order. 25,26 Recently, we showed that the breathing kagome-network compound LiScMo 3 O 8 (Figure 1a), a diamagnetic insulator because of complete localization of two d electrons per Mo within Mo−Mo bonds, is an effective anode material for Li-ion batteries. 27 The related compound Li 2 ScMo 3 O 8 (Figure 1b), with an extra d electron for every 3 Mo, also possesses a Mobased breathing kagome network, shown in Figure 1c, and is reported to be a frustrated cluster magnet, 28 with little sign of long-range magnetic order down to T = 0.5 K. Li 2 In 1−x Sc x Mo 3 O 8 , in contrast, where Sc is replaced by the smaller, isoelectronic In, has been noted to show antiferro-magnetic long-range order through muon spin rotation experiments.…”

Band-Mott mixing hybridizes the gap in Fe$_2$Mo$_3$O$_8$

“…Another mixed metal system with exciting properties and curious hybridization is Fe 2 Mo 3 O 8 -also known as the mineral Kamiokite [11]. While magnetism and magnetoelectric coupling have been widely studied [12][13][14][15][16][17][18][19], the charge excitations are highly under-explored.…”

“…Fe 2 Mo 3 O 8 is a polar magnet with giant magnetoelectric coupling, strong Dzyaloshinski-Moriya interactions, valence bond condensation (creating a cluster magnet), and the possibility of orbitally-selective transitions [12][13][14][15][16][17][18][19]. Zinc substitution, first on the tetrahedral Fe site and then on the octahedral Fe site [15,20], is of inter-est for magnetic properties as well [11,13,20,21].…”

Band-Mott mixing hybridizes the gap in Fe2Mo3O8

“…Another mixed metal system with exciting properties and curious hybridization is Fe 2 Mo 3 O 8 -also known as the mineral kamiokite [11]. While magnetism and magnetoelectric coupling have been widely studied [12][13][14][15][16][17][18][19], the charge excitations are highly underexplored.…”

“…Fe 2 Mo 3 O 8 is a polar magnet with giant magnetoelectric coupling, strong Dzyaloshinski-Moriya interactions, valence bond condensation (creating a cluster magnet), and the possibility of orbitally selective transitions [12][13][14][15][16][17][18][19]. Zinc substitution, first on the tetrahedral Fe site and then on the octahedral Fe site [15,20], is of interest for magnetic properties as well [11,13,20,21].…”