CAREER: Spin-Resolved Imaging of Correlated Electron Systems Including Cuprates and Pnictides

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NON-TECHNICAL ABSTRACTThis CAREER award funds a project to image electron spins in complexmaterials. Although electrons in metals mind their own business, barelyinteracting with each other, in so-called 'strongly correlated electron'materials the interactions of electrons drive unique properties that arefascinating and often useful. For example, so-called high-Tcsuperconductors carry electricity without loss at economically feasibletemperatures; multi-ferroic materials allow electronic data storage usinga magnetic field and magnetic data storage using an electric field; heavyfermion materials boast electrons behaving with thousands of times theiractual mass; simple sheets of carbon called graphene allow electrons tozip along as if they had no mass at all. These materials have in commonthat their electrons interact strongly, and that those interactions arepoorly understood. This project will employ a spin-polarized scanningtunneling microscope to measure the energies and locations of electronspins with atomic resolution, starting with superconductors. The projectwill also use this technology to educate three deserving groups: Harvardstudents will benefit from a new undergraduate course on scanningtunneling microscopy; local elementary school children will be invited tosee a working science lab viewing real electrons; interested citizens willbe able to browse a colorful website explaining the fascinating variety ofmaterials under investigation.TECHNICAL ABSTRACTThis CAREER award funds a project to image electron spins in high-Tcsuperconductors, both cuprates and pnictides. The common feature to theseexotic materials is that their electrons interact strongly, and there isno broadly successful theoretical language to describe these so-called'correlated electron materials'. Great strides have been made throughvarious methods of imaging the interactions of electron charges, butunderstanding has been limited by the lack of effective tools to image theinteractions of electron spins. This project will employ a lowtemperature spin-polarized scanning tunneling microscope to measure thespin-resolved density of electronic states with atomic resolution. Inparticular, a comparison will be made between spin interactions incuprates and pnictides, the only two known families of high-Tcsuperconductors, discovered in 1986 and 2008. The project will also usethis spin imaging technology to educate three deserving groups: Harvardstudents will benefit from a new undergraduate course on scanningtunneling microscopy; local elementary school children will be invited tosee a working science lab imaging real electrons; interested citizens willbe able to browse a colorful website explaining the fascinating variety ofstrongly correlated materials under investigation.