The Mott insulator β′-EtMe3Sb[Pd(dmit)2]2 belongs to a class of charge transfer solids with highly-frustrated triangular lattice of S=1/2 molecular dimers and a quantum-spin-liquid ground state. Our experimental and ab initio theoretical studies show the fingerprints of strong correlations and disorder, important role of cation-dimer bonding in charge redistribution, no sign of intra- and inter-dimer dipoles, and the decisive van der Waals contribution to inter-dimer interactions and the ground state structure. The latter consists of quasi-degenerate electronic states related to the different configurations of cation moieties which permit two different equally probable orientations. Upon reducing the temperature, the low-energy excitations slow down, indicating glassy signatures as the cation motion freezes out.
@article{arxiv.1710.01942,
title = {Importance of van der Waals interactions and cation-anion coupling in an organic quantum spin liquid},
author = {P. Lazić and M. Pinterić and D. Rivas Góngora and A. Pustogow and K. Treptow and T. Ivek and O. Milat and B. Gumhalter and N. Došlić and M. Dressel and S. Tomić},
journal= {arXiv preprint arXiv:1710.01942},
year = {2018}
}