Speaker: K. Burch, Los Alamos
Date & Time: April 11, 2006 - 1:30pm
Location: Serin 385E
Probing Hybridization: Understanding the Many Faces of Magnetism Through Optical Spectroscopy
Physics and Astronomy
K. Burch, Los Alamos
Serin 385E 1:30 p.m.
Understanding the role of local moments in metals and semiconductors has long been a challenging subject in condensed matter physics. To explore this rich subject I have employed Infrared Sprectroscopy (IR) and Ellipsometry to explore the connections between band structure and magnetism in GaMnAs and 1-1-5 family of Heavy Fermion superconductors (CeTIn5 where T=Co,Ir,Rh). In GaMnAs, this study provides conclusive evidence that the Fermi energy lies in a metallic impurity band, challenging popular theories of Ferromagnetism and our current understanding of the Insulator to Metal Transition in Dilute Magnetic Semiconductos. Our detailed analysis of the optical properties of the 1-1-5 series, revealing the hybridization gap ($\Delta$) as key to understanding their rich phase diagram. Surprisingly we find that $\Delta$ for only one of the four bands crossing the Fermi surface determines the
properties of the system.