RUI: Trapped Ion Phononics: Thermal Rectification and Controlled Heat Flow in 1D Ion Chains

Williams College, Williamstown MA

Investigators

Abstract

Energy flow in the natural world takes many forms: electrical currents, water cascading over a cataract, light arriving from distant stars, or heat leaking into a cooler to ruin one's picnic lunch. Of these, the mechanisms of greatest practical importance for our daily lives are thermal and electrical conduction. A century of technological advances, such as the development of electrical diodes and transistors, have given humanity exquisite control over electrical currents and driven today's information revolution. In contrast, our command of thermal currents - which govern 90% of energy production in the United States - remains in its infancy, yet mastering control over thermal currents could enable applications ranging from thermal logic gates to improved efficiency from photovoltaic power generation. This project focuses on developing a proof-of-principle example of a thermal diode, one of the basic building blocks for controlling thermal currents, using laser-cooled ion chains. Such chains will also enable the study of mesoscopic thermal conductivity at the crossover between quantum and classical regimes, relevant for understanding thermal currents in microscopic devices. The work will take place at an undergraduate institution; students will be involved in all aspects of the experiments and their presentation in journal articles and at scientific conferences, all of which will provide superb training for future careers in the sciences. The central goal of this work will be to demonstrate a two-ion thermal rectifier formed from co-trapped calcium and strontium ions. By coupling the two ions to thermal reservoirs at different effective temperatures formed by laser cooling, a thermal current will flow from the `hot' to the `cold' ions. The thermal current can then be extracted from the ions via laser-based fast thermometry techniques utilizing the ions' dark resonances. The sign of rectification will be an asymmetry in the thermal current under exchange of the reservoirs. Longer dual-species chains with controllably introduced disorder will also enable the study of the onset of thermal gradients across the chain using similar techniques. All of this work will provide research training to a large number of undergraduate students at all stages of their education, with a special emphasis on engaging a diverse group of students early in their undergraduate years. 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.