MSE Colloquium - Prof. Seamus Davis, Cornell University
Date: October 12, 2012 from 2:00 pm to 3:00 pm EDT
Location: Room 214, S. W. Mudd
Contact: For further information regarding this event, please contact Wesley Hattan by sending email to wjh2121@columbia.edu or by calling 2128547860.
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Seamus Davis
Cornell University

"Visualizing Creation and Destruction of Heavy Fermions"

We recently introduced spectroscopic imaging STM - a technique for mapping simultaneously the real-space (r-space) and momentum-space (k-space) electronic structure of electronic matter - to the study of heavy fermion systems (Nature 465, 570 (2010)). This approach is particularly powerful because it is the strong hybridization between electrons localized in r-space and those delocalized in k-space that generates the heavy fermions. These materials are important because they often exhibit quantum criticality, and because they may partake of the same magnetic Cooper pairing interaction as high-Tc superconductors. We carried out the first imaging of heavy-fermion scattering interference and thereby achieved the long sought direct observation of splitting of a light k-space band into two new heavy fermion bands due to the hybridization process (Nature 465, 570 (2010)). More recently we attempted visualization of the electronic structure of a Kondo-hole by imaging the electronic structure at a spinless Thorium atom substituted for magnetic Uranium atom in the heavy fermion compound URu2Si2. Surrounding each Thorium atom the heavy-fermion hybridization modulations predicted to occur at Kondo-holes were observed. Finally, by introducing another new approach - the 'hybridization gapmap' - to heavy fermion studies, we discovered intense nanoscale heterogeneity of hybridization due to a combination of the randomness of Kondo-hole doping and the long-range nature of the hybridization oscillations (PNAS 108, 18233 (2011)). A very rapid uptake of these new approaches to visualizing electronic structure of heavy fermions is now occurring across this research community; I will discuss future challenges and prospects for contributions of spectroscopic imaging STM to this research field.