We investigate displacive short-range order in pyrochlore Y2Nb2O7, which exhibits a nonmagnetic insulating state despite the presence of formally tetravalent Nb4+ (S = 1/2) ions on the pyrochlore network. Synchrotron x-ray diffraction on a single crystal reveals a characteristic x-ray diffuse scattering (XDS) pattern primarily around q = {0.5, 0.5, 2}. Reverse Monte Carlo (RMC) simulations uncover local Nb displacements along the <111> axes, leading to the formation of linear Nb4 tetramers. Our findings highlight a crucial role of molecular orbital degrees of freedom in stabilizing the nonmagnetic insulating state. This study demonstrates that RMC analysis of XDS provides a powerful approach for elucidating short-range correlations and the underlying mechanisms governing the physical properties of crystalline materials.
@article{arxiv.2511.06366,
title = {Linear tetramer formation in nonmagnetic pyrochlore niobate},
author = {Shota Nishida and Shunsuke Kitou and Shingo Toyoda and Yuiga Nakamura and Yusuke Tokunaga and Taka-hisa Arima},
journal= {arXiv preprint arXiv:2511.06366},
year = {2026}
}