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报告题目： |
New progress on Itinerant ferromagnetism and Curie-Weiss Metal in Multi-orbital Systems |
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报告人： |
吴从军教授 |
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报告人单位： |
University of California, San Diego |
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报告时间： |
6月23日下午4:30 |
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报告地点： |
科技楼北410会议室 |
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报告摘要： |
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Itinerant ferromagnetism (FM), i.e. FM of mobile electrons with Fermi surfaces, remains a hard-core problem of strong correlation physics. The mean-field type Stoner criterion neglects correlation effects and thus too much overestimates the FM tendency. In fact, even under very strong repulsions, typically electrons in solids usually remain paramagnetic. Furthermore, the Curie-Weiss metal phase above but close to the Curie temperature is also a long-standing problem exhibiting a dichotomic nature: The spin channel is local moment-like and incoherent while the charge channel remains coherent showing the existence of Fermi surfaces.
In spite of these difficulties, based on unambiguous non-perturbative studies, we proved the existence of itinerant FM phase with high Curie temperatures in the multi-orbital bands of the square and cubic lattices. We established a series of theorems proving the ground state FM phase over a large region of fermion fillings and performed sign-problem free quantum Monte-Carlo simulations which yield asymptotically exact numeric results. The critical and finite-size scalings of magnetic phase transitions are performed based on which Curie temperatures are extracted at high numeric precisions. Applications to p-orbital bands with ultracold fermions in optical lattices, and electronic 3d-orbital bands in transition-metal oxides such as the SrTiO3/LaAlO3 interfaces are also studied. |
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报告人简介： |
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Prof. Congjun Wu received his Ph.D. in physics from Stanford University in 2005, and did his postdoctoral research at the Kavli Institute for Theoretical Physics, University of California, Santa Barbara, from 2005 to 2007. He became an assistant professor in the Department of Physics at the University of California, San Diego (UCSD) in 2007, and an associate professor at UCSD in 2011. His research interests include quantum magnetism, superconductivity, orbital physics, and topological states in condensed-matter and cold-atom systems. |
