Coupled frustrated quantum spin-1/2 chains with orbital order in volborthite Cu3V2O7(OH)2(H2O)2

TL;DR

This paper develops a microscopic magnetic model for volborthite, a spin-liquid candidate, emphasizing orbital order and frustrated coupled chains, and confirms its validity through exact diagonalization matching experimental data.

Contribution

It introduces a DFT-based model highlighting orbital order and frustration in coupled chains, differing from previous kagome models.

Findings

Model aligns with experimental magnetic properties

Frustration driven by next-nearest-neighbor interactions

Magnetism arises from coupled frustrated chains

Abstract

We present a microscopic magnetic model for the spin-liquid candidate volborthite Cu3V2O7(OH)2(H2O)2. The essentials of this DFT-based model are (i) the orbital ordering of Cu(1) 3d 3z2-r2 and Cu(2) 3d 3x2-y2, (ii) three relevant couplings J_ic, J_1 and J_2, (iii) the ferromagnetic nature of J_1 and (iv) frustration governed by the next-nearest-neighbor exchange interaction J_2. Our model implies magnetism of frustrated coupled chains in contrast to the previously proposed anisotropic kagome model. Exact diagonalization studies reveal agreement with experiments.