Non-perturbative Results for Itinerant Ferromagnetism in Multi-orbital Systems
| Date/Time: | Thursday, 04 Feb 2016 from 4:10 pm to 5:00 pm |
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| Location: | Physics 0003 |
| Phone: | 515-294-5441 |
| Channel: | College of Liberal Arts and Sciences |
| Actions: | Download iCal/vCal | Email Reminder |
Abstract: Itinerant ferromagnetism (FM) is intrinsically a strongly correlated phenomenon, which remains a major challenge of condensed matter physics. Most FM materials are orbital-active with prominent Hund's coupling. However, the local physics of Hund's rule usually does not lead to the FM long-range order. Furthermore, the magnetic phase transitions of itinerant electrons are also long-standing problems difficult to handle by using perturbative methods. In this talk, I will present non-perturbative studies on itinerant FM. Exact theorems are established for a stable itinerant FM phase in a large region of electron densities in multi-orbital systems, which provide sufficient conditions for Hund's rule to build up global FM coherence. In addition, thermodynamic properties and magnetic phase transitions of itinerant electrons are studied via sign-problem-free quantum Monte Carlo simulations at generic fillings. Without introducing local moments as a priori, the Curie-Weiss metal behavior is identified in a wide range of temperatures. These results will provide important guidance to the current experimental search for novel itinerant FM states in a large class of systems ranging from the transition-metal-oxide heterostructures (e.g. LaAlO3/SrTiO3) to the p-orbital bands in optical lattices filled with ultra-cold fermions.
Bio: Yi Li received her Ph.D. in physics from the University of California - San Diego in 2013. She is a currently a PCTS Postdoctoral Fellow at Princeton University (2013-2016). Her research interests include non-perturbative approaches to strongly correlated quantum systems, itinerant ferromagnetism, novel topological insulators and topological superconductivity in condensed matter and ultra-cold atom systems.