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arXiv · 1811.00969

Prediction for the singlet-triplet excitation energy for the spinel MgTi$_2$O$_4$ using first-principles diffusion Monte Carlo

Brian Busemeyer·Gregory J. MacDougall·Lucas K. Wagner
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Abstract

The spinel, MgTi$_2$O$_4$, undergoes a transition into a dimerized state at low temperatures that is expected to be a spin singlet. However, no signature of a singlet-triplet transition has been discovered, in part due to the difficulty of predicting the energy of the transition from theory. We find that the dimers of MgTi$_2$O$_4$ can be described by a Heisenberg model with very small interactions between different dimers. Using high-accuracy first-principles quantum Monte Carlo combined with a novel model-fitting approach, we predict the singlet-triplet gap of these dimers to be 350(50) meV, a higher energy than previous experimental observations have considered. The prediction is published in advance of experimental confirmation.

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Brian Busemeyer, Gregory J. MacDougall, Lucas K. Wagner. 2018-11-02. Prediction for the singlet-triplet excitation energy for the spinel MgTi$_2$O$_4$ using first-principles diffusion Monte Carlo. https://doi.org/10.1103/physrevb.99.081118

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