Possible realization of the Majumdar-Ghosh point in the mineral szenicsite

Abstract

The Majumder-Ghosh (MG) point is a point in parameter space for a one-dimensional (1D) frustrated system where $\ensuremath{\alpha}={J}_{1}/{J}_{2}=0.5$ and the ground state is shown to be a superposition of singlet states. This leads to no magnetic order, instead the ground state is dominated by electronic dynamics, much like that of a spin liquid. Szenicsite is a natural mineral that is predicted to have isolated 1D ${\mathrm{Cu}}^{2+}$ chains and lies close to or on the MG point. In this work we use muon spin spectroscopy to demonstrate that szenicsite does not magnetically order down to 100 mK and there is an absence of a spin gap, with 1D magnetic excitations dominating. Therefore, we believe szenicsite shows the properties that would put it on the MG point and, as such, it is an interesting system for studying the properties of this quantum mechanical state.