* PHYSICS/BK21 SEMINAR *

Forming quasiparticles out of local moments, the case of heavy fermion CeIrIn5

연사: 심지훈 박사[Rutgers Univ. USA]

일시: 2007 년 8 월 29 일 15:00 ~ 17:00

장소: 물리학과 세미나실(3-201호)

ABSTRACT:

Heavy fermion materials have unusual properties arising from the presence of a partially filled shell of $f$-orbitals and a very broad band of conduction electrons. At high temperatures, the $f$-electrons behave as atomic local moments. As the temperature is reduced, the moments combine with the conduction electrons to form a fluid of very heavy quasiparticles, with masses which are two to three orders of magnitude larger than the mass of the electron. These heavy quasiparticles can undergo superconducting or magnetic transitions at much lower temperatures. Understanding how the itinerant low energy excitations emerge from the localized moments of the $f$ shell is one of the central challenges of the condensed matter physics. It requires the understanding of how the dual, atomic particle-like and itinerant wave-like, character of the electron manifest itself in the different physical properties of a material. Here we address these fundamental questions by ab initio study of a paradigmatic heavy fermion material CeIrIn$_5$, which is currently in the focus of intensive investigations. We predict the evolution of the one electron spectra as the temperature is reduced. We follow in detail the buildup of coherence, in the form of a dispersive many body feature, and its effects on the conduction electrons and optical conductivity of the material. We find multiple hybridization gaps and we link them to the crystal structure of the material. The theoretical approach, exemplified in this talk, provides a natural explanation of the multiple peak structures observed in optical experiments and the sensitivity of the 115s to substitutions of the transition metal element and may provide a microscopic basis for the more phenomenological descriptions currently used to interpret experiments in heavy fermion systems.

문의처: 민병일(054-279-2074, bimin@postech.ac.kr)