Manipulating the strong quantum spin fluctuations in triple perovskites with effective spin-1/2 triangular lattice

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Non-technical Abstract:While the rise of quantum computers may one day help solve complex problems and deliver information with unhackable security, there is lack of a material platforms for scalable realization of quantum technologies. For instance, the most interesting magnetic property of the celebrated quantum spin liquids (QSLs) is the possibility of quantum mechanical encryption and transport of information, protected against environmental influences. Despite extensive studies on QSLs, they are still far away from applications. First obstacle is the shortage of understanding of this new phase of matter. The common belief is that the strong quantum spin fluctuations (QSFs) play a critical role in QSLs but how exactly QSFs lead to QSL state or other exotic quantum magnetic phenomena is not clear. Second obstacle is that most of the studied QSLs are insulators and electronically inert, which is incompatible with an electrical circuit that relies on moving charge carriers. The grand challenge is to find a way to convert the entanglement information into mobile charge signal by “metallizing” quantum magnets. This project will take a unique approach by using strategical materials design to address these two obstacles. The project also will support the education and activities of two graduate students. The principal investigator’s educational effort is to attract undergraduate and high school students to the real world of science and technology and to motivate them to pursue careers in science by bridging the gap between research and educational settings. The main activities include: (i) bringing the lab to the classroom by integrating the exposure to the PI’s research program and research facility into existing undergraduate courses; (ii) bringing the classroom to the lab by developing a summer seminar; (iii) reach out to high school students through the Governor Summer School of the Tennessee state.Technical Abstract:This project will focus on triple perovskites A3BC2O9, in which the effective spin-1/2 magnetic ions form a two-dimensional equilateral triangular lattice. Therefore, this system fits all the requirements for maximized QSFs. The chemical substitution on A sites or C sites can easily introduce perturbations, such as anisotropy and quenched disorder into the system. Moreover, the PI also can use its “sandwich” structure, by combining high pressure, to explore the metallization of quantum magnets. The approach includes (i) crystal growth of the new triple perovskites; (ii) studies on how the QSFs react to the perturbations and how the physical properties of the sandwich structure involve under high pressure by complementary low temperature, high magnetic field, and high pressure measurements, including AC susceptibility, specific heat, thermal conductivity, resistivity, elastic and inelastic neutron scattering, and total scattering for pair distribution function (PDF). The expected outcomes will provide (i) new QSL candidates and guidelines for new QSL search; (ii) a new direction for metallizing quantum magnets and fundamental knowledge about how the itinerant electrons interact with quantum spin states.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.