报告题目：Interface and collective modes of a BEC immersed in a Fermi sea
报告人：黄博 博士
主持人：董光炯 教授
时间：2017-12-15 下午2:30
地点：理科大楼A814
报告人简介：
Career
2015-now Post-Doc at IQOQI, Innsbruck, Austria
2010-2015 Research assistant at University at Innsbruck and junior scientist at IQOQI, Innsbruck
2010 Teaching assistant at University at Innsbruck
Scientific Education and Thesis
2010-2015 Efimov Physics in an Ultracold Cesium Gas
PhD Supervisor: Prof. Dr. Rudolf Grimm and Prof. Dr. Francesca Ferlaino
University at Innsbruck, Innsbruck, Austria
2008-2009 Linewidth Reduction of a Diode Laser by Optical Feedback
MSc for Strontium BEC Applications
Supervisor: Dr. Florian Schreck and Prof. Rudolf Grimm
University at Innsbruck, Innsbruck, Austria
2004-2008 System Timing-Control Program and Atom Chip Design
BSc for the Experiment of Ultra-Cold Atom BEC
Supervisor: Prof. Ru-Quan Wang
Institute of Physics, Chinese Academy of Science, Beijing, China
2007 Thermal and density structures of H II galaxies deduced from
Undergraduate spectral synthesis based on Sloan Digital Sky Survey Data Release 5
Research (supported by Chun - Tsung Endowment)
Supervisor: Prof. Xiao-Wei Liu
Peking University, Beijing, China
报告内容简介：
The static characters and collective dynamics of a trapped Bose-Einstein condensation (BEC) can change significantly when the BEC is strongly interacting with a degenerate Fermi gas. We realize such a quantum mixture with a 41K BEC immersed in a large single-component degenerate Fermi gas of 6Li, and both elements are trapped in an elongated optical dipole trap while the interspecies contact interaction is manipulated by a magnetic Feshbach resonance between the lowest spin state of both elements near 335.08 G. When the interspecies repulsive interaction increases, the two components start to repel each other, i.e. the BEC density is enhanced while the fermions are depleted at the trap center, and finally become spatially separated when the interaction is sufficiently strong.
To study the mixture, we use three-body recombination as a probe to study the overlap between the two species for various interaction strengths and see a decrease in losses when the interactions become strongly repulsive and compare the loss rate to that of a non-condensed bosonic cloud. In a phase-separated mixture, losses only happen at the interface of the two species and are orders of magnitude weaker than that in a mixed phase of both species. To understand our loss rate results, we calculate the spatial overlap between the two components with a mean-field model. This model fits nicely to our experimental results and reveals effects beyond the local density approximation (LDA). On the other hand, we measure the frequencies of BEC collective oscillations at various interaction strengths and observe a substantial change of the frequency of the radial breathing mode. We try to interpret our observations with the Gross-Pitaevskii equation and the Boltzmann equation.
