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Dissertation/Thesis Abstract

Approximate Phase Diagram for an Extended Shastry-Sutherland Anti-Ferromagnet
by Anguiano, Michael, M.S., California State University, Long Beach, 2020, 72; 27736214
Abstract (Summary)

Previous work by D. C. Ronquillo and M. R. Peterson has strongly suggested the existence of a topologically ordered quantum spin liquid phase in the intermediate regime of the antiferromagnetic Heisenberg model on the Shastry-Sutherland lattice. There are a number of physical systems, such as SrCu2(BO3)2), ErB4, and TmB4, that are well approximated by the aforementioned model. However, realistic effects such as next-nearest neighbor spin-spin interactions could have non-trivial effects on the phase diagram or even on the existence of the topologically ordered spin liquid. In this work we modify the Shastry-Sutherland lattice by introducing the next-nearest diagonal bonds J3 to study how the system changes in response to strength variations of these extra bonds, as well as the variations in the traditional J2 bonds. We calculate the lowest-lying energies via exact diagonalization on a cluster of 24 spins, and summarize our results with a phase diagram showing regions of Neel, quantum spin liquid, and VBC phases. We then characterize the ground states by computing the topological entanglement entropy as a function of J2 and J3 using the Kitaev-Preskill construction method and discuss the order of the transitions between the different phases observed.

Indexing (document details)
Advisor: Peterson, Michael R.
Commitee: Jaikumar, Prasanth, Gredig, Thomas
School: California State University, Long Beach
Department: Physics and Astronomy
School Location: United States -- California
Source: MAI 81/9(E), Masters Abstracts International
Subjects: Computational physics, Condensed matter physics
Keywords: Anti-ferromagnets, Antiferromagnets, Heisenberg, Magnetism, Sastry-Sutherland
Publication Number: 27736214
ISBN: 9781658444125
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