报告人：Dr. Zhenjie Yan

University of California, Berkeley

时间：3月16号（星期三）下午14：00

地点：北园物理楼106

内容简介：Strongly interacting gases of fermionic atoms give insight into the workings of correlated Fermi systems, from nuclear matter to high-temperature superconductors and neutron stars. The transport properties of these systems often cannot be understood in the framework of weakly interacting quasiparticles. This talk will present our recent results on probing heat transport and the breakdown of quasiparticles in a Fermi gas with unitary interactions . In a highly imbalanced spin mixture, radiofrequency (rf) spectra of spin impurities reveal a dramatic transition from dressed quasiparticles, Fermi polarons, at low temperature to undressed particles of a classical Boltzmann gas. In contrast, in a spin-balanced gas, the spectral shift evolves smoothly to zero with an increasing temperature. Using the temperature-dependent rf spectra as a local thermometer, we directly observe a striking signature of the superfluid phase transition in a unitary Fermi gas: while in a normal fluid, heat propagates diffusively, below the superfluid transition temperature heat propagates as a wave known as second sound. From the damping of second sound and heat diffusion, we measure a quantum limited diffusivity for both modes, which display a peak at the transition temperature.

报告人简介：Dr. Zhenjie Yan is a post-doctoral researcher at University of California, Berkeley. He received his BS degree at Tsinghua University in 2014, and earned his Ph.D. under the supervision of Prof. Martin Zwierlein at MIT in 2021. His Ph.D. research focused on the many-body behavior of a strongly interacting Fermi gas. He is currently working on exploring new methods of controlling and detecting individual atoms with an optical cavity with Professor Dan Stamper-Kurn.