Trevor Bailey, Lu Chen, and Callum Jones have been named recipients of the Rackham Predoctoral Fellowship for the 2019-2020 academic year. This one-year fellowship is awarded to students in their final year of graduate school who are working on especially creative or impactful dissertation work. Each graduate program can nominate up to three students for this award, and all three of the nominees proposed by the Physics Department were selected this year.

The first awardee, Trevor Bailey, is a fifth-year graduate student working with Professor Ctirad Uher. His research focuses on thermoelectric materials, in which a difference in temperature across the material induces a voltage, or vice versa. One application of thermoelectric materials is to convert heat to electricity; for example, waste heat from automotive or industrial exhaust could be recycled back into usable energy. Copper selenide is one such material, and Mr. Bailey has worked on enhancing the efficiency of the heat-to-electricity conversion in copper selenide at high temperatures. Part of his work on this project has included preventing electromigration, or the motion of the highly mobile copper atoms in this material, which can cause it to degrade under conditions required for applications. Mr. Bailey has also worked on growing theoretically predicted thermoelectric materials. One method of growth he has used is molecular beam epitaxy, in which the atoms making up the material are deposited one layer at a time. Most recently, Mr. Bailey has worked on studying the magnetic properties of a magnetic, metallic material called a half-Heusler compound. Half-Heusler compounds tend to be good thermoelectric materials, and the presence of magnetic interactions could enhance the thermoelectric properties, making these materials more useful for potential applications.

Lu Chen, also a recipient of the Rackham Predoctoral Fellowship, is a fifth-year student working with Professor Lu Li. Her dissertation project focuses on the development of a new technique called quartz magnetometry, which uses a quartz crystal to measure the electric and magnetic properties of materials in a magnetic field. Quartz crystals are commonly used in digital watches to keep accurate time, but the measurement technique employs a special frequency mode of the crystal that has never before been used in material property measurements. The new technique provides a powerful and highly sensitive method for measuring solids at extremely low temperatures and high magnetic fields. In addition, Ms. Chen researches heat management in electronic devices. Electronics heat up during use, and too much heat generated inside the device can lead to failure. One material that can be used to remove excess heat is vanadium dioxide, which has the interesting property of transitioning from a metal to an insulator. Near this transition, vanadium dioxide becomes very efficient at conducting heat, making it ideal for electronic device applications. Ms. Chen’s research on quartz magnetometry and vanadium dioxide has been published recently in Physical Review Applied and Applied Physics Letters, respectively.

Fourth-year graduate student Callum Jones is the final Rackham Predoctoral Fellowship winner from the Physics Department. He works with Professor Henriette Elvang on developing efficient mathematical and computational methods to describe particle physics in the Standard Model and beyond. The Standard Model is the current theory used to describe fundamental particles and their interactions. Theoretically, the Standard Model could be used to calculate any quantity relating to particles and their interactions, but these calculations can quickly become unwieldy due to their complexity. Instead, Mr. Jones uses a modern approach called the on-shell method that emphasizes symmetries rather than interactions to simplify the calculations. One recent project that Mr. Jones has worked on using these methods is related to string theory. In string theory, tiny one-dimensional objects called strings vibrate, and different vibrations are manifested as various particles. In addition, string theory includes higher-dimensional objects called membranes. The membranes also vibrate—in two dimensions, they can be visualized like vibrations on a drum head—and these vibrations again give rise to particles. Mr. Jones has studied interactions of these particles using the on-shell approach and has found that the interactions have many unexpected properties.

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Rackham Predoctoral Fellowship