121/123Sb nuclear quadrupole resonance and muon spin relaxation experiments of Mo3Sb7 revealed symmetry breakdown to a nonmagnetic state below the transition recently found at TS=50 K. The transition is characterized by a distinct lattice dynamics suggested from narrowing of nuclear fields. We point out that the Mo sublatice is a unique three-dimensional frustrated lattice where nearest-neighbor and next-nearest-neighbor antiferromagnetic interactions compete, and propose that tetragonal distortion to release the frustration stabilizes long-range order of spin-singlet dimers, i.e., valence bond crystal, which is thermally excited to the dynamic state with cubic symmetry.
@article{arxiv.0805.3892,
title = {Frustration-induced valence bond crystal and its melting in Mo3Sb7},
author = {T. Koyama and H. Yamashita and Y. Takahashi and T. Kohara and I. Watanabe and Y. Tabata and H. Nakamura},
journal= {arXiv preprint arXiv:0805.3892},
year = {2009}
}