CAREER: A Versatile Quantum Simulator for Fermionic Ordering

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

This CAREER award supports the development of a novel and versatile “quantum simulator” aimed at better understanding the properties of solid materials. In addition to attributes like density and elasticity, materials have properties such as electrical conductivity and magnetism that result from the fundamentally quantum mechanical behavior of the dense gas of electrons holding the atoms together. Some of the wide variety of complex and technologically important properties of materials, such as superconductivity and magnetism, can only be understood using quantum theory. Unfortunately, the centrality of quantum mechanics to these properties means that simulating them with classical computation devices is either ineffective or inefficient. This award supports an alternative approach, wherein the awardee and his students are developing a simulator capable of modeling the underlying physics of materials using the quantum properties of atoms. In order to bring out the quantum effects in lithium atoms, they need to simultaneously cool the atoms to within one millionth of a degree above absolute zero and cause them to act like a solid material. Students will use one set of lasers to slow the atoms down to achieve the cooling, and another set of lasers to pin them in place. Critical to this award, scientists, including the awardee, have developed a technique to shake the pinned atoms, which coerces them into emulating a much larger range of materials than previously possible. This award will further scientific insight into materials of technological relevance, as well as support a new generation of students in understanding quantum interactions. In addition to supporting the training of graduate students, the award supports high school students and teachers from the Atlanta area to work in the lab over the summer on mechanical and electronic (“mechatronic”) automation tools to increase lab productivity. The skills and knowledge of state-of-the-art laboratory set up acquired will be used to develop similar tools for the high school physics lab. This award supports a novel approach to quantum simulation of materials using laser cooled, ultra-cold lithium. Many of the details of debated importance in materials relate to the Fermi surface, where the conduction electrons live. The project will employ shaken optical lattices, which allow a great degree of control over the shape of the Fermi surface. Thereby, the Fermi surface will be tuned to favor or disfavor certain types of order. Important questions about how these different forms of order can compete or co-exist can be answered, and create complex phase diagrams generated from a well understood microscope model that can be directly compared with theory. The project team will use resonant optical lattice shaking in a gas of ultracold lithium atoms to tune the Fermi surface shape. The project goals include facilitating interactions with significant momentum dependence, demonstrating two merging Fermi surfaces at a neck closing (Lifshitz) transition, and creating models of nesting-driven density wave formation in a “clean” scenario where no lattice phonon modes exist to provide an alternate mechanism. 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.