Charge disproportionation and spin ordering in LiV2O5 and NaV2O5: a distributed moment point of view
Abstract
The effects of charge disproportionation between V4+ and V5+ on the exchange interactions and related magnetic, electronic and optical properties are studied in LiV2O5 and NaV2O5. The magnetic exchange interactions between local moments on atomic sites are calculated using a linear response approach based on the QSGW band structure. While the induced magnetic moments are small on the vanadyl Ov and bridge Ob, their exchange interactions with the V are found to be larger than between V atoms. The Néel temperature TN are calculated within the mean-field (MFA) and random phase (RPA) approximations for two different crystal structures with P21mn and Pmmn spacegroups. The critical temperatures are are corrected by a quantum statistical factor of (S+1)/S to obtain reasonable agreement with experiment. Band structures, optical dielectric functions calculated using the Bethe Salpeter Equation method and spin waves are also calculated and presented for both crystal structures and both compounds. The spin wave dispersions are calculated from the classical Heisenberg Hamiltonian including magnetic moments on both V and O atoms. Besides the lowest energy weakly interacting spin waves of the two chains of spins in the unit cell, the model predicts additional high energy optical spin waves, which correspond to more complex spin excitations in which the spins on the two V across a bridge, vanadyl O and bridge O precess independently from each other instead of staying locked together according to their collinear alignment in the ground state. These show only weak dispersion and extend up to about 1 eV but we argue that these are an artefact of using the Heisenberg model beyond its validity range and would be suppressed in a more complete theory that allows for coupling of the transverse spin with longitudinal spin and charge excitations.
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BibTeX
@misc{garcia2026charge,
title = {{Charge disproportionation and spin ordering in LiV$_2$O$_5$ and NaV$_2$O$_5$: a distributed moment point of view}},
author = {Claudio Garcia and Ilteris K. Turan and Jerome Jackson and Swagata Acharya and Mark van Schilfgaarde and Walter R. L. Lambrecht},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.24263},
eprint = {2610.24263},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.24263},
}
RIS
TY - UNPB
TI - Charge disproportionation and spin ordering in LiV_2O_5 and NaV_2O_5: a distributed moment point of view
AU - Claudio Garcia
AU - Ilteris K. Turan
AU - Jerome Jackson
AU - Swagata Acharya
AU - Mark van Schilfgaarde
AU - Walter R. L. Lambrecht
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.24263
UR - https://arxiv.org/abs/2610.24263
AB - The effects of charge disproportionation between V^4+ and V^5+ on the exchange interactions and related magnetic, electronic and optical properties are studied in LiV_2O_5 and NaV_2O_5. The magnetic exchange interactions between local moments on atomic sites are calculated using a linear response approach based on the QSGW band structure. While the induced magnetic moments are small on the vanadyl O_v and bridge O_b, their exchange interactions with the V are found to be larger than between V atoms. The Néel temperature T_N are calculated within the mean-field (MFA) and random phase (RPA) approximations for two different crystal structures with P2_1mn and Pmmn spacegroups. The critical temperatures are are corrected by a quantum statistical factor of (S+1)/S to obtain reasonable agreement with experiment. Band structures, optical dielectric functions calculated using the Bethe Salpeter Equation method and spin waves are also calculated and presented for both crystal structures and both compounds. The spin wave dispersions are calculated from the classical Heisenberg Hamiltonian including magnetic moments on both V and O atoms. Besides the lowest energy weakly interacting spin waves of the two chains of spins in the unit cell, the model predicts additional high energy optical spin waves, which correspond to more complex spin excitations in which the spins on the two V across a bridge, vanadyl O and bridge O precess independently from each other instead of staying locked together according to their collinear alignment in the ground state. These show only weak dispersion and extend up to about 1 eV but we argue that these are an artefact of using the Heisenberg model beyond its validity range and would be suppressed in a more complete theory that allows for coupling of the transverse spin with longitudinal spin and charge excitations.
ER -