Emergent phases in Kitaev spin-orbital magnets

Arizona State University, Scottsdale AZ

Investigators

Abstract

NONTECHNICAL SUMMARY Magnetic materials play a central role in technological advancements in information storage in cell phones and computers as well as creation and distribution of electricity. However, when the magnetism is suppressed in these materials via quantum effects, a completely new phase of matter called "quantum spin liquid" appears. This award supports theoretical research on materials exhibiting the quantum spin liquid phase, in which the quantum spins do not order in a fixed configuration even at absolute zero temperature and perpetually fluctuate. Such materials show unusual properties that may have technological implications such as the possibility of offering a platform for quantum computation. In this project, the PI and his team will investigate new models of quantum spin liquids called Kitaev spin-orbital models. The team will theoretically design new materials that can exhibit spin liquid phase and collaborate with experimentalists for the identification of the key experimental signatures of these materials. In addition to graduate student training in condensed matter theory, this award will also support the PI's outreach efforts that involve promoting quantum literacy - understanding the fundamentals of quantum physics - at the high school level. To achieve this goal, the PI will participate in the ‘Science and Engineering Experience’ and ‘Clubes de Ciencia Arizona’ high school outreach programs to mentor high school students and organize workshops for them focused on the quantum world. TECHNICAL SUMMARY This award supports theoretical research with an aim to investigate single- and bi-layer Kitaev spin-orbital models as new platforms for the realization of quantum spin liquids that are stable to external perturbations. While the Kitaev model on the honeycomb lattice is the first exactly solvable model with a quantum spin liquid ground state, direct application of this model to real materials is limited as the quantum spin liquid state is fragile to additional interactions present in real materials. One way to remedy this challenge relies on extending the Kitaev model to its spin-orbital generalization, commonly called Kitaev spin-orbital models. The research activities in bilayer Kitaev spin-orbital models will focus on estimating the phase diagram as a function of interlayer exchange and small angle twisting via complementary analytical methods. The PI will also perform Monte Carlo simulations to investigate vison crystals (periodic arrangement of flux excitations) that are stabilized by additional interactions. Successful outcomes will provide key insights to upcoming experiments on quantum spin liquids while advancing our understanding of spin-orbital generalizations of Kitaev model. In addition to graduate student training in condensed matter theory, this award will also support the PI's outreach efforts that involve promoting quantum literacy - understanding the fundamentals of quantum physics - at the high school level. To achieve this goal, the PI will participate in the ‘Science and Engineering Experience’ and ‘Clubes de Ciencia Arizona’ high school outreach programs to mentor high school students and organize workshops for them focused on the quantum world. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.