Frustrated quantum magnets

Abstract

A class of Frustrated Quantum Magnets (FQM) is investigated using the Stochastic Series Expansion (SSE) Quantum Monte Carlo (QMC) method. Such a model is relevant to a class of rare earth tetraboride materials that display multi stepped magnetization plateaus under external magnetic field. The Shastry-Sutherland lattice was used to represent the arrangement of magnetic ions in these materials.

Previous studies showed a multistepped plateaus while plotting the z-magnetization against the external magnetic field. While many computer hours have been spent on supercomputers on trying to understand the multistepped phenomena, much has yet to be revealed.

In theory, we always choose the thermodynamic limit, but this is not possible in the real world. As such, we used Monte Carlo Simulations to assists us in understanding this multistepped phenomena. As computer hour is limited, we started using small system size, and increase it in factors related to the step level until we observe no change in the results.

The research done by Asst. Prof. Pinaki Sengupta and Keola Wierschem had produced planes of the ground state phase diagram. The diagrams showed the regions of plateaus and superfluidity state of the system. These diagrams give us an overview of the possible ground states with different parameters.

With Keola‟s help, I continued their work to produce the following plane of the ground state phase diagram. A different style in visualising the phase diagram is implemented for analyzing and categorizing regions of superfluidity and plateaus. We were also lucky enough to discover newfound plateaus in the initial stages of the project.